Please visit our Sponsors
FAQs on Acrylic Aquarium Repair and Modifications: Leaks, Cracks, Parted Seams

Related Articles: Aquarium Repair,

Related FAQs: Acrylic Repair 1, Acrylic Repair 2, & FAQs on Acrylic: Design, Scratches & Crazing, Drilling/Cutting, Construction, Solvents, & Glass Aquarium Repair, & DIY Gear 1, DIY Gear 2, Tanks, Stands, Covers, Custom Aquariums, Stands, Covers...,

Acrylic Aquarium Repair     4/15/17
Hello there and thanks for providing such an informative website! I purchased a used acrylic tank whose condition is a bit rough, it’s 150 gallons 72”x24”x20” 3/8ths thick sheet pretty standard stuff. Anyhow I could really use an expert opinion on whether this tank will require dowelling after I re-solvent the separated chemical welds.
<Yes; I would apply doweling here. My rule of thumb is anytime, with the whiting out anywhere, that more than half the joint is troubling... to do so. Plus the nearby crazing worries me.>
If so must I use cast acrylic or can an extruded rod be utilized for the dowelling?
<Either will be fine here; for this application.>
Furthermore when do you recommend using weld-on 3 versus weld-on 4 for re-solventing?
<Both are close to being about the same viscosity. I like "runnier" for tight areas, brand new material in general>
The enclosed photo is of the front upper left corner, and is by far the worst corner of the aquarium the rest of the tank is surprisingly not so bad. Thanks for providing information that allows a regular working guy to afford his dream aquarium! Thanks David
<Welcome! Bob Fenner>

Re: Acrylic Aquarium Repair      4/16/17
Hi Bob thanks for getting back to me so fast, in your response about dowelling the corners you mentioned the near by crazing worried you how so?
<Evidence of stress there... could be from poor matching of joints, uneven stand, weak acrylic.... But points to the need to add the doweling>

With the additional dowelling should I worry about the crazing?
<Less so>
I thought it was minor you can't feel it at all, but then again I’m no expert. Thanks
<Welcome. BobF>
Re: Acrylic Aquarium Repair       4/17/17

Got it, I will weld up a steel stand with a 1 ½ butcher block top to support the tank properly; dowel all internal corners, and re-solvent the bad seams. Thanks for the sound advice!
<Very glad to share. Bob Fenner>

Acrylic tank lifespan     3/30/17
Hi, I am rather humbled to ask, but what is the "lifespan" of acrylic aquariums for both larger and smaller models? I ask because I have been in the tank maintenance business for 25+ years, and some of my clients tanks are that old or older.
<A well-made system of small/er size (hundred gallons or so) should last twenty years or more if kept on a level, planar stand>
Also, if an acrylic tank starts to get the "cloudy spots" in the seams, or any other tiny leak, will those seam leaks grow?
<They will unfortunately. IF there are whited out areas that approach half the seam width, a good idea to drain, have corner doweling solvented in all inside seams>
Thank you in advance
Bill Thomas
<Welcome. Bob Fenner>

140 acrylic aquarium; concern re defects        1/21/16
So I purchased a 140 gallon Acrylic aquarium off crag list for $400. The dimensions are 60x18x30, my question is should I worry about these I don't know what to call it other than anomalies in the panes which I guess is called a joint. I have never had an Acrylic aquarium so I have no idea but I'm worried after a little research on how to remove scratches lead to reading about catastrophic failure .
Thanks Manuel
<The bit of hazing, scratching is not problematical; and the blem in the joint looks fine from the one pic you sent. Does the "whited out" area extend far into the joint? (when seen from the direct on view?). If more than a quarter way through, ahead of filling I would fill w/ a low viscosity Weld-On product as gone over on WWM.
Otherwise I'd use this tank as is.
Bob Fenner>

Re: 140 acrylic aquarium... no rdg.      1/22/16
Ok, thanks again for you input it's much appreciated . The whited out area you speak of do you mean like a blotch spot?
<Yes; these are vacuolations... areas where the solvent is/has failed twixt panes>
The panes are 5/8" thick
<Plenty thick>
, the guy I bought it from said the blotches are just cosmetic but I have my doubts.
<Can be more.... you didn't read....>

My only concern is the tank being safe to setup in my living room and not worry about walking in a small pond one day. I provided one more picture of the right side of tank.
<One last time (with a twist) HERE:
and the linked files above.... it's like a jingle. BobF>

Re: 140 acrylic aquarium      1/23/16
Got it went over it very helpful.
<Ah, good>
To get a better idea of how this happen , I'm guessing the blem is a result of the outer seam not bonding or unbonding ?
<Un; yes>
If I use the tank as is, in your opinion will it be fine until I save enough money to buy a new one with the same dimensions ? About maybe six months to a year?
<Yes; highly likely; though... as prev. stated, and listed a few times in our archives. T'were it me/mine, I'd opt instead to "fill" the whited out areas w/ solvent (while the tank is empty)... B>
Thanks again Manuel.

Acrylic Tank Question; seam going       6/15/15
Hi guys! Thanks for the website and the info--due to some (possibly overly paranoid) worry I have, I wanted to send you an e-mail about a tank I just got. Picked the tank up from someone who was looking to get out of fishkeeping, he had it for several years and never had any issues with leaks and despite being on a stand that I don't think was the best (large gap in the middle so it wasn't supporting the entire bottom of the tank, which we would be reinforcing), there wasn't any bowing going on. I think the brand was SeaClear, unfortunately only 3/8" thick which seems to be pretty standard for these mass produced tanks, and there is some noticeable crazing with a few spots that made me a little uneasy. I'm not super familiar with acrylic tanks, but I wanted to send some photos of the spots I mentioned to see if I'm just being paranoid or if there is serious cause for concern.
<The whited out area labeled Right Bottom is (too) bothersome... While the tank is out, clean, empty... I would use a water thin solvent... such as: "SCIGRIP 3 Acrylic Solvent Cement, Low-VOC, Water-thin".... applied with a small squirt bottle with needle applicator... will take just a drop... into the seam/gap here>
For as long as he had the tank, there were no issues, no leaks, bowing, or anything like that and he kept an Oscar, a Parrot, a Firefin, two Plecos, a number of pretty decent sized rocks/ornaments and a lot of substrate for several years without any issues. Am I getting worried over nothing?
<All such "bad areas" that go this deep into the seam are definitely worth  worrying about, and fixing. In this case, likely just by re-solventing the area/s... In more advanced cases by fitting in square doweling (of acrylic; check that the corner inserts are 90 degree angles; i.e. NOT concave), with heavier bodied (Weldon 16 my fave) solvent... in all internal corners...
Bob Fenner>

Re: Acrylic Tank Question       6/15/15
Yeah, the impression I was getting from your site and others was that using the two products you mentioned would help fix the problem, with the latter applying to tanks that looked worse than ours.
If we just use the Weld-On 3, how long do you think could we reasonably expect the tank to last without fear of leaks/bursting?
<IF the white out completely disappears, indefinitely>
Thanks so much for the response, Bob :D
Mark Hemmert
<Glad to share. BobF>
Re: Acrylic Tank Question       6/15/15

Is the solvent anything we could buy locally, or is our best bet to order online?
<You might get lucky and find someone who sells nearby... like an acrylic fabricator, outlet... Most folks have to order. B>

Acrylic crazing       5/8/15
Hi, I have a standard 180 gallon marine aquarium, 6 x 2 x 2. Acrylic is 1/2 inch thick with heavy Eurobracing. The tank has been running for one year.
After hearing about crazing and tank failures
<Mmm; not from crazing; no>
I noted some crazing on my tank mostly on the right seem towards the top. See picture.
<Oh! This is a seam issue, not crazing really... your MEK joint weld is partially failing. Still... it doesn't appear to be "that bad">
The tank is finally looking great and I would hate to tear it down, but can't take the chance on a failure either. Would love an expert opinion. Thanks Mark
<T'were it me/mine, I'd leave as is... IF the white-out areas move to half the seam however... In the meanwhile, I would send along this pic to the manufacturer, fabricator for their input. Bob Fenner>

Re: Acrylic crazing      6/9/15
I bought it off CL. It was 6 years old but never setup by the owner, so no info on manufacture etc.
<Mmm; and I don't recognize the design...>
Thank you for the prompt reply. It really helps.
<Glad to be of help to you. Again; I would not worry, not take this tank down. Bob Fenner, whose employee-owned corp. used to do such work>

Acrylic tank; blem., stand/level concern       12/31/14
I wanted to ask you guys a couple questions. I have a 1200 gallon 1 1/2" acrylic tank. The seems look ok with some crazing. I have included a pic at the top of the front panel. It is about 1/2" wide so it is still leaving about an inch of bonded space.
<I see this "blem"... and suggest you or someone try a low viscosity Weld-On product or equivalent... to fill in this gap>
Should I reinforce this or is this ok if the rest of the tank is normal?
<Because it is near the top, its shape, size, not likely a problem ever; but I would still try capillating in a wee-bit of solvent here. Take care NOT to drip excess... perhaps a bit of blue tape around the area lest there be run-off>
The tank dimensions are 10'x4'x4'. My last question is I talked to an engineer and my tank is level side to side but from front to back (4' side) it is almost a 1/2" unlevel.
<?! What?... I really, make that REALLY don't like this... measure the panels... length and width... is/was one side actually mis-cut this half inch?>

He said this was about an extra 100lbs on that panel but should be fairly insignificant to the rest of the tank. He said it should be fine. Do you agree with this? Thanks.
<"Should be fine" in that the tank should not catastrophically fail, yes... but if this were some tank our old company had fabricated, we would not ship it; and if I paid others to make it; I'd at the very least extract a ten year warranty against leaking or failure... if not sent it back. Bob Fenner>

Re: Acrylic tank       12/31/14
Thanks for the responses. I probably phrased the question wrong. The tank is all the same size, just my floor has a slight decline causing the tank to lean slightly.
<Ahh; still a concern. I'd be making sure the floor underneath is strong enough by far... AND shimming up whatever support you're utilizing to spread the mass of this set up about, above or below floor>
The tank side to side is level but because the concrete
<Oh! On the floor side then>
is slightly going down hill, the water level is about 1/2" higher in the front of the tank than the back. So over 4' it has a 1/2" decline. Is this a problem or was the engineer correct in saying the panel will hold about 100lbs of water extra and shouldn't be a big concern?
<It is FAR better for you to make sure the tank is level AND planar. Have you read my article re stands on WWM?>
Thank you.
<Welcome. BobF>

A Question about Acrylic Tanks    11/15/14
We just has a 150 gal custom acrylic tank fabricated for us. The one side seam has bubbles trapped in the entire length of the seam, pictured below.
<... poor technique applying the solvent, filling the gap>

The acrylic material is ¾" so I don't think this is a structural or leak issue but one of cosmetics. Is this typical of acrylic tanks or unacceptable?
<Mmm; not typical or desirable... >
The tank cost upwards of $4k.
<Well... likely to "be okay" in terms of the tanks integrity, holding together... IF only on one seam... I might have the fabricator install a support in the one/two corners (along the entire run) AND turn the tank's back to the wall (if being installed against one)>
Thanks you in advance for your opinion.
<We used to fabricate up to 2"... would not allow such work out of the shop. Bob Fenner>


Re: A Question about Acrylic Tanks    11/15/14
The tank is free standing in the middle of a room. There is some millwork under and above but out in the open.
Ray Fischer
<Uhhh! I would not then (for appearance-sake) install the corner bracing... BUT would extract a longer-term (five-ten year) guarantee from whomever fashioned this tank. Don't know what they used to "off-set" (this statement for browsers) the panels to be welded, but I would have used small piano wire sections. Cheers, BobF>

Re: A Question about Acrylic Tanks    11/15/14
Hi Bob F
So your telling me this is acceptable and I should pay for the tank?
<WITH the stated warranty, yes. B>
Re: A Question about Acrylic Tanks    11/15/14

Thank you very much for your time
Ray Fischer

Re: A Question about Acrylic Tanks... seams/solvent       11/17/14
Hi Bob F,
<Hey Ray>
Thank you for your help. The tank fabricator is stepping up to the plate. He is sending a rep up to correct the problem.
<Please do make known his and your further impressions. BobF>

Internal overflow leak     5/29/13
Hello aquatic experts,
I'm sure this question is answered somewhere on your site but it has defeated my attempts to find it. I have a built in overflow that has a small leak at the bottom. The leak is between the overflow and the tank so no water gets on the floor as long as the power stays on. But since the leak causes the overflow to equalize with the tank any power outage will drain the tank about 6 inches, which is more than my sump can handle.
<Have to get a larger sump (volume) and leave the water level down there...>
  I currently have the pump off, and closed the return valves so this can not happen but I would like to get my tank connected to the sump again. Is there a way I can seal this leak without draining the tank?
<A couple of standard approaches... there are epoxies... that can be applied/reapplied around joints, with or w/o another piece of acrylic (I take it as the material of construction... there are repairs for glass, PVC...). All require draining the tank... You may want to consider inserting an overflow pipe, pushed or threaded (if the bulkhead/through-put fitting on your tank is threaded)... Raising it/this to near the height/level of your overflow teeth>
Both the tank and the overflow are acrylic. The overflow is in the middle if the back wall and goes from the base of the tank up, with the holes in the bottom.
The leak is somewhere along the bottom edge where the overflow meets the base but I do not know exactly where.
<Again... likely just thicker, more viscous (less fluid, more molasses like) Weld-on is the route I'd go>
Thank you for your assistance.
<Take your time here... planning, containers, friends to help hand out the gravel and rock... can be done in a few hours time with all tools and materials on hand... Oh, and DO get the larger and/or additional sump for transit volume, test (unplug pump/s) to assure it won't overflow. Bob Fenner>

Acrylic tank crazing in seams – 5/22/12
First, thanks for all the useful information your site provides.  I have read the information currently on the site for acrylic tank crazing/cracking issues.  I have a 64"l x 15"w x 24"h Clear for Life tank which has 3/8" acrylic.  Bought it used so I do not know it's age.  It had only very few minor scratches, no cracks, but some crazing in the seams.
<Mmm, not crazing... but vacuolations... spaces/gaps where the solvent (during construction) didn't flow to, seal face to face. Happens when sheets aren't square, and/or not held close (enough) together while solventing>
 I have never had a take this large or an acrylic one.  Tested for water tightness before setting it up and no problems - minimal bowing when filled.  Top brace looks good.  I have set the tank up and the crazing in the seams is concerning me.
There was some in the bottom seams, but very little.  My real concern are the side (vertical) seams along the colored rear acrylic piece.  I have enclosed two pictures of the most affected seam.  I have had the tank set up a couple of months, and although the crazing does not appear to be growing, but either I did not notice the cloudy fading horizontal bands layered up the seam (blue to lighter cloudy blue), or it now has those cloudy bands. 
I really need someone else's opinion of whether this is minor or could cause a failure soon.  The hood that is one the tank is very heavy and I am wondering if this could be an issue?
<Not likely; no. This tank is good for many years of use>
 It appears to be like most tanks that
have a wooden/particle board stand and hood to match.
<Thank you for sharing. Bob Fenner>
Re: Acrylic tank crazing in seams – 5/22/12

Thanks - didn't notice my typos until I read this back - sorry.
<Welcome; no worries. BobF>

Large Acrylic Aquarium Seams- Did I Buy A Problem? 2/13/12
Hi, we recently bought a large (300+ gallon) acrylic 1 inch thick aquarium with center back overflow and nice steel stand. It has a black acrylic back, is a nice deep shape, is 30" tall and was not super cheap and is a hard to find shape (would not feel happy throwing it away or putting a free sign on it). I just noticed that some of the seams are not clear.
<I see this/these>
Many are but quite a few are not. The previous craigslist owner said it did not leak at all. We have not filled it with water yet because I wanted your feedback first. We looked for pictures that looked like ours with what to do but did not find much, so am sending the email.
I'm attaching pics for your feedback.
To describe the pictures I attached: Many Seams- quite a few look like this Middle Left- towards the bottom of the picture shows a whiter area of the seam Middle Left 2- shows the same area in the back left of the photo Middle Left 3- close up of the same area Top Seam- is a picture of an area of the top seam
What is your thought?
<I'd install square doweling (solvented) in all inside seams. Read here re:
And if repair is needed where is good in southern California (we are not capable ourselves) and is it worth it?
<See the "Yellow Pages" (analog and/or electronic) re Plexiglas/Acrylic... you'll find sellers of tools and materials, and fabricators... contact them re this repair if you don't want to attempt it by yourself... IF you know and trust a competent retailer (petfish) that does such repairs, ask them re>
And your website it a great service, we've used it before for research.
Thanks, Worried in So Cal
<Cheers, Bob Fenner, in not-so-sunny San Diego>

Clarity Plus Lifetime Warranty? (and acrylic tank resurfacing/repair) -- 01/07/12
<<Hey Garrett>>
I have recently purchased a 300 gallon acrylic aquarium from c-list for a couple bucks and thought I was getting a real deal.
<<Mmm, is often the case'¦till one sees the scratches. But even so, this can still be a 'deal' if you're willing to apply some elbow-grease. Returning the tank's clarity is not all that difficult>>
and I may have if I don't count for my labor resurfacing the tank.
My question is and it's a three part'er; how would one go about contacting the aquarium manufacturer being Clarity Plus (SeaClear, the Casco Group and so on) to attempt to cash in on said warranty?
<<If this tank has been modified or repaired (other than authorized) in any way, it's likely the warranty has been voided>>
I cannot find any contact info for them anywhere. Wondering if maybe they shut their doors?
<<Hard to say'¦their products seem to still be on offer though. You might try contacting a retailer selling their product, such as FishTanksDirect.Com>>
Second question:
Assuming I am not lucky enough to cash in on that warranty and continue doing the work myself, how clear is clear enough for acrylic?
<<'¦? You would be surprised at what 'disappears' when water is added to the tank>>>>
I have dry sanded from 120grit up to 400grit and then wet sanded from 400-4000grit and come back with polishing compound and have gotten it very clear.
<<This is likely sufficient'¦adding water will tell>>
However there still appears to be distortion from a few feet away.
<<Mmm'¦ This is from not sanding 'evenly' across the entire surface of the panel'¦or at the least 'feathering out' the perimeter of the sanded areas. Failing to do so creates what is called a 'lensing effect' and results in the distortion you are now seeing>>
I can place a book inside and still read it but can't read it looking through both panels (just a test for clarity no intentions of reading underwater).
<<Indeed'¦kind of like trying to read through two stacked glasses lenses>>
Is the distortion because I boogered-up the restoration process on the acrylic
<<A likely scenario>>
or because the tank has some age and permanent-bowing to it?
<<A less likely scenario>>
Am I worrying to much and water will fix it?
<<Possibly'¦I would test and see'¦is possible the lensing effect is not that noticeable/within acceptable viewing limits>>
(have not finished the resurface part yet to retest clarity with water, but don't want to waste my time if its going to look like poop)
Third question:
The seams of the tank in various places around the tank have turned whitish in some spots. Almost like there is frost or ice between the panels. None are very large maybe 2' at the most , but they do span the whole 1/2' of acrylic. Never owning an acrylic tank I don't know the risks involved.
<<Minimal'¦but again'¦a water test'¦>>
It would be my assumption that the chemical bond broke there just isn't leaking (have done a 2 week leak test with litmus paper on the seams to verify leaks).
<<Then you likely don't have a worry re'¦but while the tank is empty and dry you can easily beef-up these inside corners with triangular acrylic doweling>>
Do these need to be shored up with the square braces as suggested in other posts or can I take a needle with solvent and forces it in the joint? Or something along those line?
<<My choice would be the acrylic doweling'¦applied very carefully; to avoid any further marring of the viewing surfaces, with a 'thickened' acrylic solvent like Weld-On #16 or Craftics #33>>
Any and all answers and suggestion will be greatly appreciated.
<<I hope I have served>>
Garrett Crance
<<Happy to share'¦ Eric Russell>>

acrylic tank, imperfections in joints 12/16/11
hi, huge fan of this web site, essential reading for fish keepers. Think I've got a problem i need advice on, just purchased an acrylic tank 48"Lx18"wx26"h. its made with cell cast 12mm acrylic. On inspection i noticed lots of small 1/2mm bubbles on seam. there mainly on external edges but not just a couple. I've spoken to the producer and he's said its normal and wont effect strength much but I'm concerned about filling it and will the life expectancy be reduced?
<Mmm, you're likely okay here in the short and long haul. The quality may be a bit less, but this tanks should still function for decades. Bob Fenner>
Re: acrylic tank 12/16/11

thanks for speedy reply Bob, will fill it tomorrow and hope for best. Would siliconed external angle beads add any strength
<Almost none. Not worthwhile>
or am i better off leaving be so i can keep an eye for whitening or crazing on these bubbles. thanks again.
<Welcome. I strongly doubt you will have problems w/ these seams. Cheers, BobF>

180g acrylic tank... cloudy seams concern 10/28/11
I am finally getting around to setting up my 180g Clarity Plus aquarium.
I have had the tank full for the past week doing a "leak test" prior to putting in my living room without any signs of leaks.
<Good and good>
I inspected the seams, and I think they look ok and fairly clear however on the vertical front seams (where the front & side panels join) there are some cloudy / bubble like imperfections, almost looks like frost on a windshield? The spots don't run across the width of the seam itself, and there was no evidence of a "whiteout" cloudy area across the entire seam. The imperfections are more prevalent on the outside edge of the seam, but is difficult to tell how far the extend across the seam - perhaps 1/2 way in 2 small spots but in most spots they look to < 1/4 of the way across the seam.
I didn't notice the spots getting worse over the week the tank was filled.
I tried to take a photo, but given the way the front panel is rounded off as it meets the corner it was difficult to get a good picture.
Obviously with a 180g tank the last thing I want is a leak in my living room, from your experience working with acrylic is this normal and what is the risk of separation that would cause a leak?
<Some small risk>
As a precaution do you
think I should have the inside seams of the tank reinforced with 1/2" acrylic square tube by a local plastics shop?
<Up to you... for the long term; yes>
Thanks again for your time & help
<Glad to share. Bob Fenner>
Re: 180g acrylic tank 10/28/11

<Hi there again>
I mistakenly added my phone number at the bottom of the last email I sent you, please delete if you decide to post it thank you!
<Oh yes; I mean no... We don't retain or reproduce folks' contact info. w/o their express consent/urging. Cheers, BobF>

poor seam 6/5/2011
Hello; I have a 600 gal saltwater tank. One seam on a 1" X 1" acrylic 3' high corner has a cloudy look half way up. .The rest of the seam is still clear as well as all other corners. The tank is a 2 year old reef-fish with many critters so emptying it would, I'm afraid, kill some of my friends although I will if there is no other solution.
<There is none>
I was thinking of welding a strap down the seam
<This IS what I'd do... in ALL the inside seams... square acrylic doweling is available... Solvent this in place with flat sides to the two edges>
but then to make it look uniform I would have to do the same to the other corners.
<Yes... Again, best to do now for ALL inside seams/corners>
The corners have a 3/4" radius so I don't think I could wrap around the corner and get a good weld.
<INSIDE, not out>
(also I don't have the knowledge to heat the acrylic to bend it )
<Just measure carefully and cut to abut>
The tank is very odd shaped ( like looking down on an H with a tub in one end of the H and a shower on the other with the aquarium as the walls ) plus there are straps welded across the top tying each side of the H together. What I'm wondering is there a way to mend that seam without emptying the water or any other solution?
<No; not>
Does the #40 epoxy weld under water?
<Good luck w/ your project. If it were, mine, I'd get some experienced help. Bob Fenner>

240 g acrylic repair question -- 10/19/10
I've got a 240 g acrylic tank that I just filled with water for the first time and when halfway filled I noticed @ 0.5 ml of water on inside corner bottom panel seam of internal overflow box. Can I just silicone it from
the inside of box? It doesn't leak to outside of aquarium just to inside of rear corner overflow.
<You can try this... Silastic doesn't stick well to acrylic... but if it/this is only a pin-hole leak w/ little pressure... this fix might work.
Do make sure the surface is completely dry and clean ahead of applying the Silicone. Bob Fenner>

135 gallon Clear for Life acrylic aquarium, seam-dowel repair/strengthening 3/16/10
Hello everyone!
I have a problem or worry about a future problem. I bought a 135 gallon Clear For Life acrylic tank about 4 years ago. the typical 72x24x18 at 3/8" to cut cost tank. It was setup fresh for a few years and when I moved I never set it up. Well I decided to setup a ray/shark tank, until they outgrow it. When I got all of my other equipment together, I filled it, and after the system was running for a minute (literally a minute) the rear right seam blew and flooded my living room.
I got about half of the water out into my yard instead of my carpet. After contacting advanced aqua tanks they repaired that seam by adding a corner brace at the bottom and up the side.
<Yes. A/the common approach/repair>
I brought it home and filled it with fresh and it held. It did the usually bowing but I am seriously concerned about it happening again. I have read pages and pages about acrylic tanks and I can tell you that it does not have that much crazing as my 125 Uniquarium(which is a whole other problem). My
ultimate question is about using weld-on or a similar product to strengthen the seams before I set it up.
<?... only to anneal more corner doweling...>
I read one of the last questions, Re: Acrylic Tank Crack Repair/Drilling Acrylic -- 12/31/07, that someone recommended it that maybe it would apply to my situation as well. I don't want to do something that could weaken an already weak joint.
<It would to only add it to an existing/old bond>
Also, if you do recommend it, after it has cycled transfer my inhabitants of my other tank to and do the same to the Uniquarium. As I mentioned it is a lot worse off where the crazing goes completely to the interior of the back panel of the sump area.
<I would NOT simply apply solvent to a crazed area... DO look into sealing square acrylic rod, cut to size, in the inside joints>
I have other questions about the sump setup and return of the 135 but until I read those articles I will leave them alone.
Thank you for your time.
James B
<Do "chat" w/ others who have done this modification/addition... perhaps have them help you one on one. Bob Fenner>
Re: 135 gallon Clear for Life acrylic aquarium, leak repair f' 3/17/10

Thanks for the direction! I contacted a local Plastics store and they carry Weld-On and will cut pieces to fit the interior dimensions to Weld-On to. No pun intended. In the corner where the overflow is, would I want to adhere the joints that are in direct contact with the water(the show side) or opposite?
<All inside joints>
Would it be wise to do this to the bottom joints as well, while I am at it?
In the end I want to jump to a 180 Hex
<Unsuitable shape and volume>
for the shark and rays but until then, I'm stuck.
James B
Re: 135 gallon Clear for Life acrylic aquarium... repair and system for Chondrichthyans -- 03/20/10

Thanks for the direction! I contacted a local Plastics store and they carry Weld-On and will cut pieces to fit the interior dimensions to Weld-On to. No pun intended. In the corner where the overflow is, would I want to adhere the joints that are in direct contact with the water (the show side) or opposite?
<... all inside joints need to be done>
Would it be wise to do this to the bottom joints as well, while I am at it? In the end I want to jump to a 180 Hex for the shark and rays but until then, I'm stuck.
James B
<You sent this before... A hexagon shaped system of this volume will not work for these fishes. BobF>

Acrylic Tank Repair Question -- 12/14/09
I recently purchased a 4ftx2ftx2ft ½' thick acrylic aquarium. It was made by a local who claimed it was leak proof.
<<I'm sensing this is not the case'¦>>
Well I took it home and it leaks around the bottom in one of the corners and about 6-8' along one side bottom seam.
<<Uh-oh'¦sounds like reason enough to return it to me>>
I can also see a lot of little bubbles in the seams. As well he didn't square up the tank perfectly and one of the sides sits out 1/6' off the bottom sheet. I am wondering if I should try to use some Weldon 16 and go over all the seams or if I should just get rid of this and find another?? It is brand new but leaks!!!
<<If the joints have been well enough assembled originally to keep this tank from simply bursting apart when filled, you can likely salvage it by solvent-gluing some angular acrylic rod along the seams (there is such made for this type application, see the Net re). I would suggest not trying to 'spot-fix,' but rather, glue the filler-rod along the entire inside bottom perimeter. Although'¦being a new purchase, why not return it for a refund/replacement?>>
Matt Thomas Utah
<<Happy to share'¦ Eric Russell SC>>

Livestock Acrylic Tank Leaking 10/2/09
Hey Crew. I have an acrylic tank that is holding livestock that is leaking. I've been reading through the site and only see suggestions on sealing leaky tanks when they're dry. Is there a solution to seal an acrylic tank when it has water in it?
Ryan Mullinax
<Not really Ryan... Some "not real" repairs can be made short term... wedging a piece of flush square stock (rod) into the area of the seam leak... with Silastic... but really... the tank needs to be dried, resolvented. BobF>
Re: Livestock Acrylic Tank Leaking 10/2/09

Ok, thank you Bob. I really appreciate the knowledge and experience that WWM provides the aquatic community. It has benefited me greatly over the years.
<Ahh! Am very glad for this. Cheers, BobF>

1" thick acrylic - Can we fix it? 9/27/05 Hello, I couldn't find a similar problem to mine except ...leak leak... leak. I have a very large 500+ gallon tank. It's 1" baked acrylic on all sides. I have saltwater in it and have had it for like 6 - 7 years. It's completely built in to a wall and is supported on a steel structure. We noticed some water damage on a piece of quarter round that was trimming it and when we removed the trim water started spurting from a pin hole leak. The trim was actually holding it in check some what. I don't want to try and remove the whole tank from it's location as it will cost major in carpentry. Will this acrylic cement (northcoastmarines) work for this type of leak? How does this type of thing happen after all these years? Kim <This tank can likely be repaired... in place. Do look into square "doweling" (this is sometimes only flush/ninety degrees on two of the four sides... You must make sure the flush sides are affixed to the corners. What needs to be done? Drain, clean the tank entirely, cut the doweling to size to fit in all corners (yes, including the sides), and solvent in... The extra bit of acrylic in the corners won't be obvious in time. Cheers, Bob Fenner>
Re: 1" thick acrylic - Can we fix it? 9/30/05
Thanks so much but where does one find square acrylic (I assume not just plastic?) "doweling"? Kim <Should be available, as well as solvent/Weld-on and cleaner from a large/r plastics distributor in your town... or mail-order... Use your "Yellow Page" directory, the Net to find. Bob Fenner>

Cracked acrylic tank 9/20/05 Well Bob, You were right, only give it time....I've got a new one for ya. My crew and I were installing a new 36" x 30" x 36" acrylic tank from AAT today. As the tank was being set down on the floor, one of them lost their grip for fear of getting their fingers pinched. The right front corner of the tank hit the bare concrete floor from about 2 inches up....that's when I heard that unquestionable cracking sound. I saw my profits disappear before my very eyes. However, upon inspection, it wasn't nearly as bad as I thought. The crack is actually in the bottom plate about 1/4" in just beneath where the front panel (front and sides are one piece with bent corners) is welded to the bottom panel, about 6 inches from the start of the right corner radius. This crack extends from the bottom surface upwards about 3/4" in an arching pattern, almost like a rainbow...but not nearly as pretty, and finishes back at the bottom surface. Its a pretty clean crack and does not go anywhere near where there would be water. I figured that because it directly underneath the front panel, that even if it extends further over time, it would eventually dead end into the front panel and because its almost dead center under the front panel, that there would be plenty of material to keep it from leaking. Your thoughts on this ???? Scott C. Wirtz >>>Greetings! Sorry it took so long to get back to you, things are crazy for many of us here on the "crew" and tons of queries coming in. Bottom line, it's impossible for any of us to say for sure about your tank. I had a similar thing happen though to a 300 gallon tank, and it was just fine. Good luck! Jim<<< <<RMF would still run a bit of Weld-On (of lower viscosity) into the cracked area>>

Need advice on separating acrylic sheets... 8/27/05 Hi Bob, <Ed> My name is Ed Ruiz. I'm in SLC, Utah. Seeing your vast experience in the hobby and working with acrylic I hope I can get some advice from you. <I see> I recently acquired a lot of 1/8 and 1/4" acrylic sheets (24"x48") that had apparently been stored under less than ideal conditions. I find that the sheets are still with their paper masking on, but between each two sheets there is a yellow or blue textile material that is holding them together. My theory is that they were heavily stacked (too many sheets atop each other for a long period of time - <In the heat...> I got them for free) and the masking textile's adherent has bonded rather strongly. I have not insistently attempted to separate the sheets and would like your opinion, advice or suggestions. I will use the sheets to build aquariums for a hatchery project I am working on. Ed Ruiz <Very hard to separate... inserting long, thin metal strips between and prizing apart is likely your only option... though this will very likely scratch through the protective masking... Have you tried speaking with folks in the acrylic business? Manufacturers of such do have websites... I would get their input before proceeding. Bob Fenner>
Re: need advice on separating acrylic sheets... 8/30/05
Thanks a lot Bob, your suggestion is exactly my wife's' and makes sense. <Ahh, good company> As to the acrylic manufacturer's or vendor's websites, they're more interested in selling me a product for taking the paper masking off. This tells me they did not pay much attention to my enquiry in the first place. I'll go with your advice. Ed <Please make it known how this goes... Years back I tried to do this... with piano wire and a strong friends co-help, jamming thin metal strips twixt the sheets... and getting the old masking off... what a lot of work besides! I would listen to the acrylic manufacturer's, distributor's advice re this. Bob Fenner>

Acrylic crack repair, opportunistic/typical Moray behavior 11/11/05 I just bought a used 55 gal hexagon acrylic tank. I was moving it around trying to determine placement when I realized there is a crack in the top panel. No point in finding blame now, I just want to know if I can save it or take this as a loss. <Mmm, can likely effect a simple repair here> The crack, definitely not crazing since I can feel a separation, starts from a corner round of the large cutout and extends about 3 inch toward one of the six sides. One more inch and it is going to hit the side edge! I've been reading about using Weld-On and applying an acrylic panel to the crack. <Yes> Also is drilling a hole at the end of the crack going to stop it? <Not likely useful, necessary> Can I get Weld-On at Home Depot if I were to try this? <Best to seek out from a "Plastics" supply... look in your local Business Yellow Pages Directory re> Should I worry about this crack since it is only on the top panel? <Mmm, not much to worry about, but I would solvent it closed> The tank is a standard 55 gal hex 24x24x28. It's funny how things go wrong and just seem to spiral even more. I bought the tank intending to make it a new home for my white-mouth eel about 15in, who has managed to eaten two smaller fish. Well he attacked and ate my 6-7 inch lunare wrasse last night. I couldn't believe he was able to swallow the wrasse or even catch it. What a sight! Thanks <Welcome... an easy project/fix... Bob Fenner>

Repairing acrylic leaker 3/7/06 Hello, We are searching for someone who can fix the leak in the seam of our large (8'W x 4'H x 2"D) acrylic salt water tank. <<Eeek!! A difficult challenge at the least!>> The owner has said that he sign a waiver that relieves the repair person of responsibility if the repair does not hold. <<While there are several ways that this can be repaired, no sane repair person will guarantee this work. The best looking and safest repair will require emptying the tank, cleaning out the defect and filling the void with a two part polymerizing adhesive. A cheap and aesthetically non-pleasing repair could be made by gluing an acrylic splint inside the defect with two-part or solvent adhesive after cleaning the area with sandpaper. >> The leak is small and is coming from the front left seam, about half way up the tank. The tank currently is filled to below this level and still has fish in it. Can you recommend anyone that could take this sort of job on? Regards, Jennifer Ferguson, Woodwork Creations <<I don't know of anyone to recommend. Beware that any repair does not address why this occurred in the first place... was the tank properly built to begin with? Is catastrophic failure imminent? Was the stand out of level? Personally, I would strongly consider replacing the tank with one built by a reputable builder. Best Regards. AdamC.>>

Leaking Acrylic Sump...Silicone Not the Answer - 12/12/06 Hi and thank you all for your support and knowledge. <<Hello...is our privilege to share>> I have had my reef tank for over a year now with good success. I am attempting to build a custom-size sump inside the stand of my 125 gallon running reef. I purchased the 3/8" acrylic and had it cut to size so the fit seems to be good. I used Weldon-3 in all of the seams. I then let it dry and used Weldon-16 to form a bead around the seams. <<Hmm, shouldn't be necessary if the pieces are bonded correctly with the Weldon-3, but won't hurt either. If you really want to "strengthen" the corners/seams, you could cement in triangular shaped corner braces (these are offered/can be found "pre-made" on the Net)>> I filled the sump with ½-inch of water and the water leaks out of the seams. <<Mmm, perhaps the "fit" was not as good as you perceived. For the Weldon-3 to work properly the joints must fit precisely to allow the cement to be drawn-in by capillary action>> I tried to put another heavy coat of Weld-on-16 and let it dry overnight. This also leaked. <<Hmm...just spreading it over the surface isn't likely to help as you've discovered, but if you can "force" this thicker bodied cement in to the joints you might be able to fill the gaps/leaks. If the leaks are many/large you will probably have to either cut the pieces apart and recondition the mating surfaces...or have new acrylic cut/prepped and start over>> The acrylic shop said I should use 100 percent silicone to fix the leaks because it stretches. <<A poor suggestion/option in my opinion...the silicone will not adhere well to the acrylic and though this may seem to work at first the silicon will eventually fail and leak...probably when you happen to be away for an extended period>> I read on your website that silicon is not the best answer. <<Correct>> Do you think this will work only for sealing the water and not for the structure of the sump? <<A poor solution for the former and disastrous for the latter>> I also noticed the Weldon-16 does evaporate so the seal does become much thinner when dry. <<Yes, the cement shrinks as it cures>> Thank you. Darrell <<I would try the thicker cement again, using a finger run along the joint to force it in (do make sure everything is "completely dry"). If you aren't able to seal the gaps this way then your best/safest option in my opinion is to remove this sump and rebuild/start anew. Regards, EricR>> <If this fails, RMF suggests securing a length of doweling (acrylic) cut to fit in the corners (I'd do all inside seams while you're at it)... With the Weld-On... Make sure and examine the doweling closely... it is often convex on two sides... you want the two flat sides against the current acrylic panels.> Acrylics, leaks and silicone? 1/17/07 Hello<,> I have a question. <<Hello! We got answers!>> I have a<n> older large acrylic fish tank<.> <I>t has several leaks on the bottom where the seam is<.> <<Yeeow! Talk about a bummer. Older, meaning "out of warranty"? >> I tried to silicone the outside but it made the leak worst <worse.> <<Two things. One: You don't ever seal leaks from the outside. It just doesn't work that way. Two: Acrylic needs to be welded to make a seal, using solvents, not goops. A popular method of bolstering every seam in your acrylic tank is to use acrylic dowels (square) and bond them to every seam. This procedure and more available at: http://www.wetwebmedia.com/acrylictkrepfaqs.htm >> <H>ow does <do> I fix this<?> <T>hanks. William. <<You got it, W. -Graham T>>>

Cracked Tank Hi there Bob I just cracked the bottom of my 180 gallon acrylic tank. Its okay it was empty. The crack maybe about 10"long. I would like to repair this problem if possible. Someone had mentioned to use "Weld On (I forgot the number) and attach a new piece of plexi-glass to the bottom, he also said that even if I glued the new piece on to the bottom the crack may continue to grow until it reaches the edge. <Yes... I'd plan on this... you can likely make a good repair by solventing (actually the process here... not gluing) another thinner sheet of acrylic onto the bottom of the existing one... over the crack and all else.> To remedy this problem I thought about drilling a small hole at the two ends of the crack to stop the crack from growing. Do you think this is a good idea? or do you have any other suggestions? I look forward to your input, <Do ask the folks at acrylic fabricating shops in your area, over the Net what they would do as well. I would solvent a piece onto the bottom and router off the edges. Bob Fenner> James

Cracked acrylic tank Do you see anyway of repairing this type of thing? Could I drain the tank down and try some sort of glue? Is there anything I could try before giving this thing up completely? <Sorry to hear of this major problem. I would contact an acrylic manufacturer about repairing this tank although I hold little hope for repair. You would be safer just getting a new tank. At the very least I would empty this tank ASAP and follow the suggestions from the last email. You don't want to put this off until the whole tank spills on the floor> Thanks for your patience with me. :) <No problem...That's what we're here for! David Dowless>

Acrylic tank-? I have built a corner tank with bent corners( had a fab company bend) which cost a pretty penny. I tested it out and there was a very small leak so I went back and applied more solvent and tested again, no leaks. I have had water in it for about 3 weeks just to see if there would be leaks after a period of time and there were none. In some of the seams though there is some air bubbles I have tried to fill them in with solvent but it does not seep into the bubbles leading me to believe that the edges are sealed. Do you think that these bubbles could present problems in the future or what do you think? <Likely not a problem if it hasn't been so to date. Bob Fenner> Thanks for the info, James Wesley

Acrylic tank leak Hello. I recently purchased a used 125 acrylic tank and it has a leak. There is a crack on the bottom right near the front of the tank. It does go all the way through the tank and that is where the leak is. I was wondering if I could glue another piece of acrylic or Plexiglas along the bottom of the tank (inside) all along the front edge. If that will work, what would you use to glue it? Should I use crazy glue and activator on the crack first? Please help!!! <You can solvent (not really a glue... as there is nothing left between the melded materials) a piece of acrylic here (look for "square doweling" at an acrylic outlet (it's only truly flush on two of the four sides, and you want to fit these two against the existing panels). Look for Weld-on products for solvent. Bob Fenner> Thank you, Ron

Tru Vu (acrylic tank re) Repair Howdy, <Hi there> I am very glad I located your site and appreciate the valuable information you offer. I am in the process of repairing a 55 GAL Tru Vu acrylic aquarium which has some minor leaks. <Very unusual... I sold these tanks for several years... none were defective, or became so> I am concerned because I used the traditional method for a glass aquarium and the tank is acrylic. Last night I applied DAP 100% Silicone Aquarium Sealant to the length of the interior joints. <Oops> Do you happen to know if Aquarium Sealant is going to work or if I need to get out a razor blade and start all over with the Weld-On product you mention in your postings??? <You do need to cut out the silicone and use the solvent. Bob Fenner> Please advise. Sincerely, Dan May

Help!! Tank blow out! Bob I have a tank that is 45 13/16 inches wide by 94 1/2 inches long by 33 7/8 inches tall One of the long sides blew out due someone putting their full body weight on the top while retrieving a fish. It first just popped the seam by a couple of inches and this guy said he new how to repair acrylic tanks. But as you can imagine he has disappeared. Now I have no one who can repair my tank. Desperately seeking an acrylic tank repair person in Downey, California. Sincerely, JC Benavides <The tank can be repaired... should be drained, dried, and a square dowel inserted in the (I would do the whole inside edges) inside corners... take care to look carefully at and MARK the outside edges of the doweling that are curved (IMPORTANT: Note that only two of the four dowel edges are flush, the other two are concave...) and all solvented into place. Bob Fenner>

Tru-vu built-in overflow question I just got a used Tru-vu 100 gallon long (60x18x20) tank with 2 overflow on each corner. Question is internal overflow size is about 6x6 do you know how much gph is rated? I could not find this info from Tru-vu website... <What is the diameter of the through-puts? You might call them as well> I was thinking about using 1140gph external pump on this tank but maybe this overflow draw more water than 600gph... <? What?> Also due to moving this tank (forgot to take off bulkhead during move) on both side near overflow area I have crack (not near by edge but near by internal overflow L shape area) which is about 2 inch (Both overflow area affected) <Bunk! Happens all the time.> I put 1/2" tick (5x2 and 3x2)acrylic outside of overflow L shape and inside overflow square shape acrylic (2x2) and glue them with tape plastic's glue do you think this will be enough?.... <Should be... I hope you're referring to having solvented pieces over the cracked areas and holes and re-drilling them> once I have about 100lbs liverock 100lbs live sand and water... I am getting worried... <I would fill and test it... outdoors> Maybe I should send you some pictures... Thanks Chris <Bob Fenner>

Help! Acrylic Tank Leaking 07/02/05 Hello All! <Hello Tammy> Have been rabidly searching your site (lots of great information here) for about 45 minutes. I've found a few suggestions to the problem I'm having, but was still a bit fuzzy on the execution. (one recommended using dowels) The short short version is this: I have a 110 gallon acrylic tank. Used for Saltwater. It is only about 4 years old. I bought it new. It has only been moved once since setup - I emptied it entirely and had it moved by pro's. It has been in this apartment for 18 months without incident. Tonight I decided it was time for the water change and drained off about 30 gallons. The front has always tended to bow - but I was assured by the folks at the store that this was Ok. I suspect something about the weight change made a seam leak - because all of the sudden I had a steady drip-drip-drip in 4 places under my tank. (anywhere the stand was drilled or even seamed it leaked through) And before I got the wild idea to try and improve the water quality - there was no leak. (I'd been under the tank changing the filter pad and carbon in the sump first - so I'm certain of the "no leak" report). So Yikes! So after deciding that all future tank work should be done during normal business hours, I flipped over some Rubbermaid bins, wiped them out - and started transferring water from the tank and the fish. I now have an upside-down playpen over the bin safeguarding the fish from my three inquisitive cats and 3lb dog. I've got the air and heater running in their bin, so I think they're Ok for now - though certainly not liking the close quarters. Where should I start? Are acrylic tanks typically warranted? Do you expect I'll get anything other than a "good luck" if I phone the store? I know I'll need to scrub out the tank now - anything that you would recommend to make sure that it's completely clean for repair? Usually I just use my scrubby on a stick and lots of elbow grease... but since I have the chance to take it down and really go to town on it now - didn't know if you'd recommend something. Once I've got it clean - Where do I begin to look for help locally? I believe the leak is in the bottom seams because I got down to less than 5 inches of water and still kept dripping. Is there something I can do myself? I really hadn't budgeted for a tank replacement - and I'm afraid this is my first leak. The fact that I'm on the 3rd floor and got thru the whole incident without leaking onto the folks downstairs has me reasonably confident that I could follow DIY instructions should you have any for me.... :) Also - I'm a little worried that the leaking could damage the structural integrity of the stand... Is that being over-cautious? Or do I have more problems? My father will come over tomorrow and help me lift the tank down for cleaning and I'll get a better view. Maybe could put the hairdryer on anything still damp? Thank you SO Much in advance for your help! And Happy 4th of July! Tammy <Tammy, you need to start at the store where you bought it. Most tanks have at least a five year warranty. At the same time, email the tank manufacturer about the leak problem. Most will repair or even send a new one upon receipt of the defective tank. James (Salty Dog)><<RMF would actually start by filling the tank up outside... with newspaper under it, trying to see if it is actually the tank itself leaking... very likely it his a hang-on device instead.>>
Re: Help! Acrylic Tank Leaking
Hi Salty! <Hello Redhead> Yeah, well you would think they would stand behind the goods, but the store where I bought the tank has changed hands - and the new owner indicated that he thinks that the guy that they bought it from was hiring local acrylic shops to build tanks - as opposed to selling tanks from national manufacturers. The guy was a little dodgy as far as when I would mention looking for my warrantee paperwork, he would just say that he was sure whomever made the tank was certainly out of business. (which I loosely translated into - I'm not honoring a warrantee?) Then the guy sat and wanted to sell me a new tank, new stand, and then he tried to flirt. No game either. Don't get me started. I considered telling him that I was flattered, but that I was in a relationship and that my boyfriend was an attorney - loosely translated, You'd better honor my warrantee or I'll sue cause I have free legal. LOL! <I'm thinking when a store is sold the new owner isn't responsible to honor any warranties, especially since he didn't make any money on it.> But I really didn't want to continue the conversation. Just awful. Instead of staying on point about my tank, kept talking about what a pretty redhead I am - (my hair is DARK Brown) Doh! Lousy service and just no game. :) Ugh. My tank is a 110 gallon - measures 48 inches long, and 18 inches wide front to back, and 30 inches tall. It doesn't look like Tenecor makes a standard tank with those dimensions. Oh! And Thanks for the tip on the self drill -vs.- ordered drilled. Important Safety Tip. Now if eBay is a marker of what's out there - the folks making tanks like mine brag that they're using the 1/2 inch - not that crap 3/8 that a lot of people try to get by with. (dunno if that's true - that people use the 3/8, that is) Tenecor does show a 140 tall: This model features bent (seamless) front corners. Includes a clear acrylic top with filter slots, access hole(s) and matching lid(s). Dimensions are 60"L x 18"W x 30"H Price: $913.00 While I can't find any documentation on their site as to the thickness of the acrylic, I did find a posting on another site talking about the thickness of acrylic to be used... I've included the post content below, but the gent says that his company uses 1/2 inch thick acrylic for tanks up to 30 inches tall and 600 gallons. He also mentions recommended/Ok "bow" measurements. What to expect with glass and acrylic. Dunno if it's correct - but thought I'd pass it along as well in case your interested. Tomorrow I plan on calling my LFS that I trust - and then calling their suggestion for an acrylic shop. I'll pass along the prices and info that I get in case it's ever of any use to you or yours. :) <If you don't live in a big town it may be difficult to find an acrylic shop willing to build an aquarium and guarantee it for a reasonable amount of time. Keep in mind if you are or will be keeping corals, the deeper the tank the more wattage you are going to require. James (Salty Dog)> Thanks again & Happy 4th! Tammy

(Damaged) Acrylic tank assessment 7/4/05 I am sorry this is such a long post. I just don't know what exactly is pertinent information, so when you know enough just stop reading. Reading the posts made me think really hard, and try to be perhaps too observant. I posted here because you seemed to know a lot about tank integrity. <Okay> I brought home a free acrylic (I think, are there other plastics for tanks?) <Mmm, really only very small ones... acrylic/s have many names, are about all of the same composition> tank today. It is a TruVu brand, 16 deep 18 wide 60 long. There are cracks in the top and I don't know the owner (neighbor of an ex-boyfreind), so I can't get the history of the tank. It looks like it belonged to a fraternity (stickers and spray-paint and graffiti). My ex- did say he was told it doesn't leak. <Actual cracks or just crazing? Can you feel breaks in the material? These are indicative of cracking> I am afraid it will fail. I am not concerned about a slow failure, I am afraid that some of the cracks will just split with no warning after the tank is in use some time. I also see what I think is some crazing. <Ah, I see> I haven't filled the tank to test it because I wonder if I should repair it first. The link to the repair story is broken, so I couldn't read it. <Unfortunately there is no such piece... just haven't gotten around to writing it...> If there is a quick easy fix that may hold this tank together, I will do that first. <It may be that the cracks can just be ignored (fill this tank outside and see how it does), otherwise, the solvent used to weld the tank panels together may be used to anneal the cracked portions (call, write TruVu re Weld-On...). At worst, another panel (thin) of the same size, cut-outs may be solvented to the top/cracked one> CRACKS: These may have been produced by heat, as I read in other posts. My reasons for thinking so are that the top of the tank is warped, and there is a small area of the top that looks like it may be air bubbles. Does acrylic "Boil" from heat? Also, the edges of the cracks are warped and do not match each other. <Warping is common... these tanks bend quite a bit with use/time... boiling is very bad> If the cracks were caused by heat, might the tank be compromised to the point that it will fail, because the top is an important structural member? <Doubtful, but a possibility> My reasons for thinking it is not heat is I do not see any blackening or discoloration. Also, one crack actually extends down the side of the tank about an inch. Could this crack be from an impact? <Yes, most likely... am starting to have glimpses of "Animal House"> I haven't filled the tank to test it because I wonder if I should repair it first. The link to the repair story is broken, so I couldn't read it. If there is a quick easy fix that may hold this tank together, I will do that first. There are four cracks in the top of the aquarium, they all run from a corner of the large cut out to the side of the aquarium. <These are best repaired per above> The two in the back run from the side cutout to the 1-1/4 diameter hole, to the back of the tank. One CONTINUES down the side of the tank about an inch, this portion of the crack is not perpendicular, but actually at an oblique angle to the tanks surface. <Also best repaired> The tank top has two rectangular cut-outs, two smaller rectangular cutouts, six 1/4"D circular holes, and 2 circular holes about 1-1/4 "D. One of the 1-1/4 inch holes is not really circular, it looks as if a smaller hole was drilled off center of the larger one, however the edges are nice and smooth, so I don't know if these holes were homemade, or poor quality control of the manufacturer. But the crack is not located near this bump. CRAZING: It is a really sunny day and I noticed when looking obliquely at the tank outside that there was a glittery sheen inside the acrylic. It seemed to be pretty uniform throughout the back surface of the aquarium, and I did not see any direction to it, just little spots of glitter. I could not see them on the other sides of the aquarium, but this could be because I did not turn the tank to the same angle. I suspect that it is crazing. (If not, what could it be?) <Likely crazing... though could be marks from solvent, local pressure or heat stress> I cannot see it at all when the aquarium is viewed straight on. And I don't think I could see it in indoor lighting. Is a certain amount of crazing a normal occurrence? Does it happen in every tank? <Is common> USE: When I first saw the tank, I thought that it wasn't very useful for a display tank. Now I am thinking that it actually would look pretty funky as a type of urban community tank. What do you think of this idea? Thank you, Mary <If you have the time, interest, worth trying to effect a repair. Bob Fenner>
Re: Acrylic tank assessment 7/6/05
Thank you for your reply. I was unsure about how to weld the cracks closed. The edges don't line up, and in some cases, the irregularities of the edges get in the way of realigning the acrylic. I took the tank into TAP plastics today. They suggested that I drill a small hole at the end of the crack before I weld. This will relieve any stress at that point from the misalignment. <Interesting> This makes sense. (Lucky that all the cracks end one inch from the top.) It is consistent with the reason that larger diameter corners are stronger, the stress is distributed over a larger area. <Yes> The weld-on #16 cost $3.05. The piece of scrap would have been $1, but he threw it in for free. Must have felt sorry for me, trying to save such a pitiful tank. He should only see my car! LOL! <Likely> He thought the warp on the cross member would not affect its strength, and that I don't need to reinforce it. <Okay> He had no idea about the crazing unless it was a solvent. I suppose its possible the gut tried cleaning it with something weird. But I really don't think so, it is so evenly distributed. <Is just "stress" over time mainly> I just wanted to share with you the idea of drilling. Wow a 75 gallon tank for $3.05! I'll let you know how things go with my experiment. <I'd appreciate this> I will drill the holes, wash the tank (soap and water he said) <Mmm, no... avoid soaps, detergents... toxic to aquatic life, hard to remove, leave a film... water and vinegar, possibly straight vinegar (white) for "scale"...> and weld a piece of scrap over each crack. I am toying with the idea of welding an acrylic divider in the middle to compartmentalize it into two tanks, but I haven't decided yet. <Mmm, worth considering... but hard to change later> I would prefer a removable divider, but since the acrylic will flex, I don't know how I could do this. <There are commercially made dividers, but these are a bit flimsy for this sort of tank> Right now I really could use smaller tanks. Well its time to stop blathering, and see if this idea will hold water! Mary
<Real good. Bob Fenner>

Become a Sponsor Features:
Daily FAQs FW Daily FAQs SW Pix of the Day FW Pix of the Day New On WWM
Helpful Links Hobbyist Forum Calendars Admin Index Cover Images
Featured Sponsors: