Repairing a 90G Acrylic Tank, w/ Epoxy   6/23/09
Hi,
<Hello>
How are things?
<Fair to middling... though most all the Crew seem to have evaporated...>
I'm a big fan of your site, I read the FAQs weekly, and whenever I'm wondering about something aquarium-related. The advice and tips are just great, and easy to understand.
<Thank you for this>
Well, I wanted to ask about repairing a 90G acrylic. Actually, I want to ask if I made the right repair, or if I have managed to mess it up.
I bought a used 90G for a really good price ($100, versus multiple hundreds new), but it came with a catch. The back right corner had a small crack, and I needed/wanted to plug two drain holes that had been cut into the bottom of the left corner overflow tower. (The tank will sit on a very low stand, with the sump next to it, not underneath it, so the holes had to be plugged.)
I had read about Weld-On, looked for it all over town, could not find it, and finally thought - how about marine epoxy?
<Mmm, messy, and unsightly... but could work with glomming on to edges of patch pieces... applying inside...>
I had read articles and posts around the web about how reef-keepers use marine epoxy to attach frags in their tanks. That made it seem non-toxic enough to try. And I also thought, maybe incorrectly, that since marine epoxy is used to repair boat hulls, it has got to be strong enough to take the relatively smaller water pressure in a 90 gallon tank.
So I made the repairs with Loctite Aqua-Marine Epoxy (waterproof epoxy).
The corner crack was about 3/8th of an inch long, curved, in the back panel bottom corner, but didn't cross the three-way corner joint. The tank held water even with the crack. I just didn't trust that the corner would keep holding water over time.
To brace it, I cut the corner from a small acrylic sump that came free with the tank, then epoxied the corner inside the tank to cover the corner where the crack was. On the outside of the tank, I epoxied two 3" squares on each side, layered so that their joint was off-set from the tank's corner weld, and then coated the bottom of the corner with more epoxy.
To plug the overflow holes in the other corner, I cut a square of acrylic and epoxied that down, coated the seams, and coated the bottom underneath the tank with more epoxy.
Then I let everything cure for a day, and filled the tank. After a day with water in it, it's holding water. No sign of leaks, and the epoxy is rock-hard to the touch.
Maybe it is just a case of second thoughts and after-the-fact jitters, but do you think this repair will hold long-term?
<Yes I do>
I'd like to be prepared in case I need to tear down the tank quickly and make a fast repair, if a leak springs, or if I should do something more before trusting that the repair is good.
Thank you,
Matt
<Thank you for sharing. Bob Fenner>

Re: Repairing a 90G Acrylic Tank - 6/23/09
Hi Bob,
<Matt>
Thanks for getting back to me. I appreciate the reassurance. It was the first time I've tried to repair acrylic.
<Is a neat medium... I do wish the useful solvents were more readily available... Weld-On does have some sterling products>
Just for fun, last night, I put two pieces of scrap acrylic together with a dab of Loctite Marine . . . then tried to pry them apart this morning . . .
they're not coming apart.
<Uh no... the acrylic will break first>
Hammering and prying just damages the non-epoxied part. The part with the epoxy wants to stay where it is. That's with only 12 hours of curing. Looks like this will work out. It's not as pleasing to the eye as Weld-On would be, I guess, but that's fine, the repairs are not in a visible part of the tank.
<Yes>
Thanks for your help!
Matt
<Certainly welcome. BobF>

Crack In My Round Acrylic Tank…Can It Be Repaired? – 10/15/08
I have a coffee table acrylic tank. There was a small crack by the upper lip since I have had it but it never affected the tank.
<<Okay>>
Recently we moved the tank and my “help" decided to do the final move by themselves and extended the crack down about four inches into the tank.
<<Uh-oh>>
I can keep it half full (which is still pretty good) but I would like to use the whole tank.
<<Indeed>>
Is it repairable?
<<It is…though you won’t be able to “hide” the repair>>
I thought of maybe silicone and then a strap around the top so the crack could not spread but, I don’t know.
<<Absolutely not… Silicone does not adhere well to acrylic…you would very likely end up with “water on the floor”>>
I s there a way to fix it or should I just cry and say goodbye to it?
Lorraine
<<There is a way to repair this tank, Lorraine…though the crack/repair will remain visible, but this does not seem to be an issue with you. The tank can be repaired/bonded using solvent cement that will “recombine” the molecules making the repair as strong as the original unbroken Acrylic panel…if done correctly. Acrylic solvent cements come in different viscosities for different uses, what you need for this job is the “water-thin” solvent used to bond Acrylic by “capillary action.” You will also need a special needle-applicator to apply the solvent. You can find both of these on the NET…one source is here for the solvent (http://www.craftics.com/products.cfm?category=80), the 2oz bottle should suffice for your repair…and you can get a needle-applicator here (http://www.craftics.com/products.cfm?Category=2). To make the repair, draw the crack tightly closed (perhaps with the aforementioned strap) and apply the solvent with the applicator so that it is drawn completely in to the crack (you may need to do this from both sides). This takes a bit of finesse as applying too little too slow will seal the edges of the crack without getting thorough/complete coverage, and applying too much to fast will cause the solvent to run down the side of the tank and leave a “permanent” mark (practice on some scrap beforehand if possible). After the solvent is applied, leave the strap on the tank until the repair has cured well (at least several hours). If the crack has pieces that have been broken away and it does not close and fit together tightly the water-thin solvent won’t work, but there are “thickened” solvent cements that can be used to make the repair (e.g. – Craftics Cement #33). You can also use the thickened cement to fix your crack if you are not comfortable with the capillary method (apply to the break before drawing it together with the strap), but the repair won’t be as “clean” as with the capillary method. Do also query the NET for more detailed instructions on repairing cracks in Acrylic. This may all seem a bit overwhelming but if you take your time, research the methodology, and do a bit of practicing with the applicator you should be able to effect a reasonable repair. Regards, EricR>>

How level does a tank have to be ?/ Acrylic Repair
Tank Leveling/Sump Repair 2/15/08
Dear Crew,
<Eric.>
You’ve helped me with my various setups in the past, including this one, and was hoping you can answer this. I am setting up a 65 gallon AGA RR tank. The tank sits on a heavy duty wood stand that was built by the original owner.
The setup sits on a concrete basement floor ( no carpet, etc. ). The tank is level lengthwise, but the front is about ¼” lower than the back.
<Not good.>
If I am correct in assuming that that is a problem, what is the best way of leveling the tank?
<Shimming, cutting long tapered pieces to give support over the entire weight bearing areas of the stand.>
Should I shim it or run a length of ¼” wood under the front.
<The latter, along with long shims down the side to distribute the load.>
If shimming, do I place shims the whole length, and along the sides where they are now raised?
<Yes, just combine this with the continuous piece in the front.>
The shims will probably protrude from under the tank. Can I trim them?
<Yes.>
The setup also came with a DIY acrylic sump which has a leak.
There are no visible cracks in the vicinity of the leak so I am assuming it is a bad seal. I’ve been told to use Weldon to repair it but can’t find it locally.
<This sounds like a leaky seam. WeldOn will fix this, do be sure to thoroughly clean the area of any salt or other residue first (just rinse with water).>
I have found a hobby shop that carries a product called Tenax 7R, which the owner says he used to repair his acrylic skimmer. Would this be ok to use?
<Yes, this will work fine.>
Thanks,
Eric
<Welcome, good luck, Scott V.>

Acrylic Tank Crack Repair/Drilling Acrylic – 12/30/07
Hello,
<<Greetings>>
I am writing to ask a question regarding repair to the top panel of my 110 gallon acrylic tank.
<<Okay>>
I just got the tank really cheap and it is not filled yet. The tank is 60lx24hx18w and is made of 3/8” acrylic.
<<Mmm…too thin for this “height”…you will have some bowing>>
There are 2 access holes in the top, and there is a crack running from the right side of the hole on the left to the back side of the tank.
<<Not good, as you are/should be aware…most acrylic tanks gain much of their structural integrity from the perimeter brace around the top>>
My idea is using JB Weld on the crack, then covering it with 1/8” or ¼” acrylic I have cut to size, and gluing that to the top to completely cover the crack on both sides so it won't separate again. Please let me know if this is a good approach to this problem.
<<A good plan… And although pulling the crack together and “fusing” with the solvent would likely be enough (the cracked piece would again become “one” if done correctly)…I would suggest an oversize piece of 1/8” acrylic on both sides to “sandwich” the crack for that extra measure of reassurance>>
Also, the tank has a built in overflow which is cool, I plan to keep the skimmer and heater in the sump so they aren't in the display tank.
<<Sounds good>>
My problem with this is there is no access hole near the sides for wave-makers I have and would like to put at each end of the tank. I know acrylic can be drilled easily, but drilling how close to the ends is safe, and how big a hole should I drill for the cords?
<<You mean the perimeter brace at the ends of the tank, yes? I would keep at least an inch from the tank sides…and make the hole just large enough to pass the equipment “plug-in” through. Do use a “bi-metal” hole-saw…and practice on a piece of scrap to get a “feel for it”…>>
I am paranoid about weakening the top support for this tank after hearing the horror stories about how badly a tank this height made out of this thickness acrylic will bow when filled.
<<3/8” acrylic on a 24” high tank is going to bow…period>>
Thanks for your time,
Chris
<<Happy to assist. EricR>>

Re: Acrylic Tank Crack Repair/Drilling Acrylic – 12/31/07
Hello again, and thanks for your quick response.
<<Hi Chris…and quite welcome>>
To update, I called around today and had no luck at glass shops finding my solvent weld,
<<I generally turn to the NET for such>>
but one of them recommended I call a company here in Erie, Pa. called Polymer Marketing.
<<I see>>
So I called and spoke with a guy named Mark, not only did he wait around for me to stop by after work to pick up the Weld-On acrylic glue.
<<Mmm…not a “glue” but a solvent (Methylene chloride and methyl ethyl ketone [MEK], I believe)…it creates a solvent “weld” (breaks down or “dissolves” the acrylic which allows it to recombine molecules)>>
He gave me a 15 minute or so demo of exactly how to use it, then didn't even charge me for the solvent or the applicator bottle with syringe- man, now that is customer service!
<<Indeed!>>
Anyways, we sketched out on paper my tank and the crack and he felt that this product along with the 1/8'' piece of acrylic will be fine.
<<Excellent>>
He also gave me a good tip to pass along- taking the applicator bottle and going over the back and bottom seams the aquarium has to reinforce and strengthen them, and fix any weak points.
<<Agreed>>
The way this stiff sucks itself into the smallest opening is amazing, pretty nifty product.
<<Ah yes…. In its least-viscid form, the solvent requires the parts be fitted very closely to allow the solvent be drawn throughout the joint by capillary action. Heavier, more jell-like versions of varying degree (made so by the addition of acrylic resin) for other applications are also available and quite handy to the DIYer>>
He also felt that with these precautions since the tank is used, that the 3/8 acrylic will be plenty strong enough for 110 gallons (I am crossing my fingers).
<<Oh yes, quite “strong enough” to hold this volume of water indeed…but not at 24-inches of depth without “some” bowing>>
So I will be setting up this week, I appreciate your help, thanks guys.
Chris
<<Happy to share…good luck with your project. Eric Russell>>

Should I silicones seams on acrylic tank? 11/3/05
Hi,
I recently purchased a used acrylic 125 gallon aquarium. It is in a very good shape. It does not leak. But just in case I am thinking about sealing seams with silicone anyway. Do you think it's a good idea?
<Mmm, no>
I'm wondering if silicone sealant might damage acrylic.  Thanks for the great site!
<Welcome. Silicone in acrylic seams/corners doesn't provide much strength (and in between surfaces not often enough)... Acrylic doweling can be fitted, solvented into corners if there is a need/desire. Bob Fenner> 

Acrylic gluing... plugging holes.   1/22/06
Howdy folks,
<Paul>
quick question about my tank.  I have two bulkheads in my 90 gallon reef tank that I don't want to use anymore.  They are on the back of the tank, one near the top and the other near the bottom.  Can I remove the bulkheads, then get two small squares of acrylic and use Weld-On glue to cover up the holes?
<Yes>
Will they hold once the tank is full?
<Hopefully, yes>
  How big should the squares be?  
<An inch or more beyond the hole diameters>
On the outside back, there will be the openings where the holes used to be.  Should I add something on that side in case?
<Could, but not necessary>
Is there another way to close up the holes?  One bulkhead is 1" threaded, the other is 3/4 non-threaded.  Is there some sort of plug that could be put in there.  
<Yes... a piece of pipe in the non-threaded one with either a threaded or not terminus with a cap... the threaded one with a threaded cap, Silastic for "pipe dope">
What if I just cut the pipes (the ones coming from each bulkhead) from the back and cement them up with a PVC cap.
<Could be done>
  I could leave strainers on the inside of the tank.  It would be kind of a dead spot in terms of water movement (only
an inch or two deep though), but nothing would get in there.  What do you think?   What would you do.
Thank you very much
Paul
<If I was very sure I'd never want to re-use these through-puts I'd solvent the covers over, if not, cap them... Bob Fenner>

Glue and acrylic tank question(s)   3/31/07
Hello;
  I have an acrylic dispenser box that was originally used for storing soap at an "earth friendly" store. My spouse convinced me I should try it out for an aquarium (it was free). Originally I thought this was a bad idea but we set it up and tried running it with a few goldfish. They are thriving in the tank after six weeks. It's about 40 gallons in very tall, slim proportions.
  A couple of questions maybe you could help me with:
  First off, I apologize for using my goldfish as test subjects--I don't normally do such.
   1) Is six weeks long enough to be able to say it's not leaching anything toxic into the water?
<Yes>
  (I have many species of FW fish: cichlids, catfishes, loaches, ghost knife and I may creep over to the marine side eventually.....)
  2) It has some permanent ugly lettering on the back. I'm thinking of 'gluing' sand to the inside of the back panel as a background. Would Weld-On work to make the acrylic tacky, allowing the sand to stick?
<Mmm... I would not use this... for fear of weakening, ruining the panel... I would affix whatever you'd like on another thin sheet of acrylic and mount this, just place inside against the back...>
Or do you know of something else I can use, like a spray paint or glue? I expect it will be permanently there.
<Mmm... there are some epoxies that are non-toxic (once-cured) that you can use here... Check with the "Plastic Store" where you buy the scrap (hopefully from their bin of such... to save money)>
  Thank you very much for your time and expertise, best regards, Anna
  PS. I tried to register to WWM chat forum to ask my questions but was unable to.
<Am going to cc Zo here re... We're all friends, associated in that way, but only he "administers" WWF. Bob Fenner>

200 gallon tank (acrylic repair)
<<Greetings,>>
I was reading also something about drilling small holes on the bottom where the side and bottom connects and fill those holes with the #40 solvent along with sealing the inside of the tank; is that true????
<<I've never seen an acrylic tank built this way, although I can see why one might consider this stronger than a typical 90 degree joint. For certain, these holes would need to be precision drilled - too close to the outer edge, and the material will be weakened. Too close to the inner edge and the tank will likely leak.
Cheers, J - >>

Re: 200 gallon tank (acrylic repair)
When I push the side and bottom together, do I put the #40 glue
<Not a glue... a solvent... melts the panel material together.>
on the inside and the out side on the tank. Is the #40 better that the #3 and #16.Below is what I saw in the article on the web site...
1) Clean the wound.
2) Push the crack together.
3) Glue with #3 solvent to make a good seal.
4) See if the fracture extended into the sidewall and seal that if needed.
<Depends on the width of the gap... if so wide you can actually see light through the space, a more viscous model would be better... In actual practice, it almost never matters... but if the gap area can be "squeezed" together by laying the tank on its side, placing a bunch of weight (finally a use for those encyclopedias!), I would do so. Bob Fenner>

Re: 200 gallon tank (acrylic repair)
I did ask one of the people there and they told me it wouldn't work but if I was to use it I would need to inject it on with a syringe...
<Please read over WetWebMedia.com using the search tool at the bottom of the homepage... with the terms "acrylic", "Plexiglas", "aquarium repair"... You need a version of the "whole picture" which you will not get by the current process. Bob Fenner>

Re: 200 gallon tank
How do I put this stuff on, because I hear that it is some powerful stuff....
<Ask the folks you buy it from... read the label... not difficult. Bob F>

Re: 200 gallon acrylic tank repair
Do you know if this Weld-On 40 stuff will work on a 200 gallon tank as well....
<Yes... this is what many (if not all) fabricators of acrylic aquariu

Plexi glass glue
Hi there once again,
I have a question about the type of glue people use to put together plexi glass. 
<Most folks use a commercial acrylic solvent... like Weld-On>
I hear that the best way to glue two pieces together is to use a solvent called Methylene Chloride. 
<This is a principal ingredient. Toxic, flammable, not generally available to the public.>
can't seem to find it in Home Depot or Lowe's. Do you know where it might be available? 
<Check with the businesses listed in your phone directories who sell or do plastic fabrication>
I also wanted to ask if you know whether this solvent (Methylene Chloride) can be used to glue plexi
glass+regular glass together, or is it just for plexi glass+plexi glass?
<Only the latter>
On another note, I'd like to thank you for responding so quickly, and for being real informative. It's advise like this, that I wish I had for everything I come across. Your help is greatly appreciated. Thanks, Hamilton, Riverside, CA
<Glad to be here helping. Bob Fenner>

Re: plexi glass glue
Thanks for your help, but I'm not quite sure about what you meant by (only the latter). 
<The last statement... these solvents are only for acrylic to acrylic bonding>
Can you describe this in another way? And is (Weld On) safe for fishes. Well I guess it is since you said everybody else uses it. Thanks for your help.
<Safe after cures (a day or so)... it actually "leaves"... melting/melding the Plexi as one piece. Bob Fenner>

Bonding Silicone/Lexan Plexiglas
Could you tell me if silicone will attach Lexan Plexiglas to a glass aquarium or if you can only attach glass to glass with silicone?
Thanks,
Amy
<Silicone will weakly bond Acrylics, but are not to be trusted in aquarium applications of any real size/depth. Solvents for this purpose are the route to go. Bob Fenner>

Gluing acrylic
Hi,
< Hi. >
I am building an acrylic sump.  I have bonded the pieces together using a chemical that welds the acrylic.  I was planning to use 100% silicone at the joints to add extra strength and help guard against leaks, but from what I have seen here at WWM it is not recommended. < No, but I have built lots of acrylic items and I use a very thick (like honey) acrylic and make a bead all along each edge. > I found a product called Lexel which is supposed to be clearer and stronger than silicone.  Has anyone at WWM heard of this or have any experience with it? < No I haven't. But if you are using an acrylic weld like Weldon 4, try just going over each seam with something like Weldon 16. > Here is an online brochure for the product: http://www.sashcosealants.com/home_improvement/pdffiles/lexel_brochure.pdf
Thanks, < May want to swing by a local plastic shop in your area to see what products they cover. >
Dave
<  Blundell  >

Acrylic questions part 2 3/31/05
Thanks! I'll try the flush cut saw. Does the Weld-on seal as well? The reason I ask is that my tower extension pieces aren't completely perfect. Should I bond it with Weld-on and seal it with silicone? Thanks! Clint 
<IMO, Silicone has no place for bonding or sealing acrylic. It just doesn't adhere well. Weld-On #13 will bond as well as fill and seal small gaps. If you try to fill large spaces (greater than about 1/8"), bubbles will form, making a weak unsightly joint. In order to avoid this, you can fill larger gaps by applying the #13 in several light layers. Just a warning... Although Weld-On #13 will work great for the application you described, is meant for "hobby" type applications and should never be used for joints that need to hold much pressure. The pros that assemble sumps, tanks, etc., use #3, which forms extremely strong bonds but since it is watery thin, it requires perfectly machined joints. Best Regards. AdamC.>

Appropriate acrylic adhesive for reef tank
Hello,
<Hi there>
I purchased an adhesive (Devcon Plastic Welder) for my DIY skimmer and I have a quick question regarding any problems with this adhesive.  Will this adhesive leach any harmful chemicals after it has cured 24 hours?  Any input will greatly be appreciated.  Thank you.
David
<No worries... their MSDS: http://www.tapplastics.com/uploads/pdf/MSDS%20Devcon%20Plastic%20Welder.pdf
Once cured there is none left... not a glue... but a solvent. Bob Fenner>

How to unstick acrylic from plywood 7/18/05
Hi! I have just finished the building of an acrylic aquarium and as I was putting solvent cement
<Not a cement, just a solvent... melts the material together>
in the bottom joints from outside the tank, it ran and now the aquarium has stuck with some plywood pieces I used to support the tank from below it. What could I do to unstick them? Thanks. Giannis
<Unstick your sentences with spaces... and use (gingerly) putty-knife et al. hand tools to remove the wood... is going to be ugly where all were joined... can be sanded, buffed... Bob Fenner>