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>

Acrylic DIY supplies 6/13/05
Hello, I've been searching on your site for some recommendations for acrylic or plastics.  I want to make a black acrylic box open in the bottom and top with a slot in the middle to hide my Turbelle pump in the aquarium.  The question I have is where can I find a supplier?  Are the easy to find where I live, Dublin, CA or is there one you can recommend on the internet?  I'm looking for the black acrylic.  Thanks, Brent
<Most major metro areas have an acrylic supplier.  Check your local yellow pages under "plastics - sheet, rod and tube".  If you don't find someone local, do search for the websites of commercial plastics or US Plastics.  Both sell retail online.  Best Regards.  AdamC.>

Acrylic aquarium construction 7/14/05
I don't know which is the best way to hold the acrylic pieces together in order to glue them and construct my acrylic aquarium. Could you help me? Thanks. Giannis
<Building acrylic aquariums is generally NOT a do-it-yourself project.  Special solvent cements are required, and the joints between the panels have to be perfectly machined to fit.  There are specialized techniques for using spacers in the joints to allow the cement to enter the joint, and then removing the spacers to make a perfect seam.  Clamps and jigs must be used to hold the panels in place until the cement cures.  I strongly suggest doing a lot of research or leaving this project to the professionals.  Best Regards.  AdamC.>

90 gal aquarium
Hi. Like to say that there is some great info on the site.
<thanks kindly>
Im in the process of scraping some money together to build a 90 gal saltwater aquarium. I plan to make it out of 1/2" acrylic. Dimensions of 48"x18"x24".
Calculator says it should be about 90 gals. Im also gonna glue in a top brace for added support.
<will certainly be necessary. And are you working from specs with deflection tolerances of the material that you've bought or are you just building a hand grenade? <G>>
My question is, can I build a 180 gal with the same materials and same dimensions except the width being 36"? 
<While I am not an expert on acrylic, I can tell you that glass aquaria wider or taller than 30" cannot safely be built without a four sided capture (welded angle iron/steel, etc). And since 1/2 glass suffers less deflection than acrylic, a 180 will 1/2 acrylic is unlikely to be sound without very intrusive bracing if at all>
I'd like to give my silver Pacu a little more room to grow in.... What do you think?
<I agree... the Pacu needs much more room. Anthony>

SMALL DIY Tank
Dear Bob,
Most of the help I can find on the web is for REALLY large DIY tanks. I am interested in constructing an equally small one.
I am trying to go the least technical route b/c I have limited experience with tools but always want to try.
I would like an aquarium about 10"d x 18 or 20"l x 10.5"h, and I would like it to be lighter than glass and moveable (not while full of water). This is kind of like a short 10 gallon-- Not an available aquarium size.
<Okay>
I am wondering if I could make such a tank out of 1/4" Plexiglas, with a wood frame.
<Yes, could be done>
From what I've read, I understand that the plexi-to-plexi bonding would require something like Weld-On.
<Yes, or similar solvent>
What about bonding the plexi to the wood frame?
<Only for looks in this size, shape system. You could use a smear of silicone to hold the wood together and to the plexi>
Or is a frame not necessary for strength of the Plexiglas?
<Correct>
If my project is even possible, could you please help with a general description of the steps that should be taken in constructing a small tank with plexi and wood?
<Measure, cut the pieces, tape or clamp the pieces in relative place, squirt/place the solvent... let cure for a day...>
I can handle plexi, glues, wood, staining, nails and screws, but I'm afraid I have trouble with anything much more technical than that (marine plywood, epoxy, fiberglass tape...).
<Not necessary to be/get too involved>
Thanks so much for your help. Your website and FAQs are really helpful. I hope I can do you proud :)
<You have my friend. By being, expressing yourself. Bob Fenner>
Jill Petersen
Atlanta, GA

Building Acrylic Tank
Dearest WWM Crew,
<Hi Shawn>
The best piece of advice I got when I asked about beginning in the marine aquarium hobby was READ READ READ. Thanks to your site I haven't had to go far to log over 100 hours of reading just on your site in the last two weeks.
I've kept fresh water tanks since I was a young child and have been very successful at it, breeding everything from livebearers to some quite difficult tetras.
I've decided to start with a small semi-reef environment to experience the basics with plans to build a much larger than normal system in the next year. My problem arises with probably what I figured to be the most basic of formulas and was hoping that since I haven't found it anywhere else on the net or your site that maybe in your all-but-omnipotent knowledge someone there might be able to help me out. Is there a specific mathematical formula for finding the pounds per square inch exerted by salt water? 
I hope that made sense, lol, I know that water as it pertains to aquariums exerts more force on the top of the aquarium as opposed to the bottom, my problem is finding a formula for figuring out what material tensile strength I need to build a specific sized aquarium...any help you could offer would be greatly appreciated. Sincerely Yours, Shawn King, AKA reefrookie
<Yes, there is a formula for figuring out the thickness the material should be based on the height, length, etc. These formulas are specific to the various types of materials, glass, acrylic, etc, and subgroups of these based on formula or proprietary differences.
Many of the acrylic manufacturers offer product fact sheets containing this information as it is specific to their material. I would start with the manufacturer of the material you want to use. Craig>

Acrylic
Hi guys, quick question. I am in the process of making an acrylic sump. Had everything cut.. sides, dividers and have all the glues ready, but I screwed up a couple pieces tonight trying to take just a little bit off the sides (and now I need some new pieces),!@##*...bad night. Here lies the problem.
There is no place in my town to get the thickness I was working with. So I had to order everything to begin with. My sump dimensions are... sides 30"x16" and the ends are 16"x16". Was using .177" or 3/16" acrylic and even had some 1/4 from another time. The only place that sells acrylic has it in .100" or 1/10" do you think this is to thin for my sump?
<Too thin for me... unfortunately... not enough bonding surface... and will bow too much... I would hold off till you have the 3/16" material>
Will still use 3/16 and 1/4 baffles/dividers, probably 3 of them in the sump. Let me know what you think. Thanks again, Bryan
<Patience my friend. Bob Fenner.>

Building acrylic tank
I just found your site and have been looking around it. Very nice, I plan on looking more.
<Okay>
I was trying to find a formula on how thick to make an acrylic tank. I noticed in the /dessysfaq2.htm page you talk about 1/2" vs. 3/4" on a 24" tall tank. I've got an idea for a tall tank, but not sure how thick to make. I had a few companies quote the tank but some say 1/4" some say 1/2". I understand about the bowing being reduced with thicker material but eventually there must be a minimum thickness decided by a formula.
<More like "general guidelines... there is some "fiddling" with these rules of thumb depending on a few factors... length, earthquake proofedness, surface/top bracing... quality of material used (this does vary)... I would likely go with 3/8" and maybe opt for a bit thicker material for the bottom... 1/4" will bow too much... and thicker all the way around is too expensive/rich for my blood>
Can you tell me where I can find this formula? Thanks, Steve Larson
<Due to the litigiousness of this society, I doubt if anyone will/can refer you to such... I'd check out the systems made for resale, go with at least what they are made of. Bob Fenner>

My Acrylic Aquarium
Dear Wet Web Crew,
I am discouraged.  After reading today's FAQs, I am concerned that my new acrylic aquarium is under-engineered.  My 110"L x 45"H x "38"W
aquarium is being constructed with 1" acrylic walls (7/8" actual thickness), 1/2" bottom, 3/4" top.  Bob's advice was to use the same material thickness for top/bottom as walls.  Further search for FAQs on acrylic aquarium construction lead me to conclude that 1" material may be inadequate for 45" height (salt aquarium).   
<Mmm, I would have upsized the bottom... and looked into the cost of thicker material for the sides, front, back>
Is this design unsafe?
<Likely will be okay if placed on a good (strong, planar, level) stand>
Am I going to be faced with excessive bowing?  
<Subjectively... up to you to decide. If you're mainly going to be viewing head-on, likely not too bad>
The top has not yet been glued on, so still have an option to reduce height (although I'm sure at great expense).  What is the maximum recommended height for 1" acrylic?   
<About four feet... the bowing question is a matter of the "run" (length) of the system as well as height>
I'm hoping for reassurance that the existing design will pass engineering muster.  At this point, safety is a greater concern than bowing - but I really need frank advice.
<Should be fine. Bob Fenner>
Thanks in advance.  
Steve

Re: My Acrylic Aquarium (stand)
Bob,
Thanks much for your reply.  Making this kind of investment is unnerving.  Your response is reassuring, but I can see that I now have
more work ahead of me to ensure the provision of flawless base support (stand).   
<Yes, absolutely critical.>
I plan to use a single layer of concrete foundation block for the stand with 1.5" of plywood between block and tank.  Concrete blocks will
provide contiguous support under tank accept for areas where 4x1.5" bulkheads and associated plumbing run the length of the tank.   
Bulkheads are planned to be cut near the edges of the tank (leaving about 2" of material between holes and edges).  Any concerns here about
stand or about placement of bulkheads?
<This whole apparatus is set on a concrete foundation? I would use a "water level" (the tank itself) to make certain of its planarity. Please see here: http://www.wetwebmedia.com/tksstds.htm>
  Given my 1/2" thick bottom, am I introducing significant additional risk by cutting holes for bulkheads?
<Yes... If this tank has not been assembled yet, I would have this bottom made of 1" material. Much to say here... IF a tank of your dimensions was built with the sides, front and back panels atop (as opposed to on the sides) of the bottom, this would not be such a concern... but cutting through the bottom for throughputs, and having to leave space around these to fit plumbing... makes me uneasy. Our companies used to fabricate acrylic aquariums as well as installing hundreds made by others... in Southern California... where the ground shakes occasionally. I like to shy on the conservative side here. I would either NOT drill the holes in the bottom (and instead make them near the top back edge) OR secure a thicker bottom. Bob Fenner>
Thanks again!
Steve

Re: My Acrylic Aquarium
Bob,
I am grateful for the advice.  The four walls of the tank are 'resting' on top of the bottom and are glued in this fashion.  Given this assembly technique, would bottom holes be acceptable?
<Not for me>
  Could I reinforce around the bulkhead underneath the tank by gluing an additional 6"x6"x1/2" plate (thus creating a 1" section in places where the bulkheads pass through the bottom)?
<Unfortunately no. Have seen this tried time to time... too much likelihood of these added pieces joints failing. Bob Fenner>
Thanks and regards,
Steve

Re: My Acrylic Aquarium
Bob,
Thanks yet again for your response.  I see your point, and I have resigned myself to the fact that the meager thickness of the bottom leaves me with no alternative but to formulate a different approach to plumbing.
<Yes... this tank will hold some 825 or so gallons... with water weight of 6,600 or so pounds...>
If you have any patience remaining for me, I'll share a bit more detail about my original design, offer a possible contingency in light of the
issue above, and then leave the door open for any suggestion(s) you might have.
The aquarium is designed to fit an available space in my home.  I am dividing an unfinished storage room in the basement with this aquarium.  Walls will be constructed to frame the aquarium, and one half of the space will be finished as the viewing area for the aquarium. The other half of the room (behind the aquarium) will serve as the pump room, filtration area, work area, etc.
<Good idea to have plenty of space.>
The visible area from the viewing room is 9 feet (but an alcove area actually extends several feet beyond the viewing area).  Given that my local aquarium manufacturer was charging me for full 10 foot sheets of acrylic, I decided to build the aquarium 10 feet long with a 1" acrylic wall divider at the 9 ft mark and a second 1' wall at the 10 ft mark.   
The intent here was to use the last foot as a sump that would enable me to draw water from the bottom of the tank, flow into the bottom of the sump, and then overflow into pipes 1-2" below the surface of the sump (i.e. tank water line).  This would allow me to effectively circulate water to the bottom of the tank, draw unfiltered water from the place where waste and detritus naturally accumulate, and achieve the benefits of a surface draw without any visible pipes or plumbing in the main tank.  If I spring a leak in my plumbing at any point down-stream, the tank will not drain below the level of the surface feed pipes.  The only risk to the system is obviously the plumbing connecting the main tank to the sump (a leak here will drain the tank).
<Yes>
Original Design:
My original design was based on a UG filter to draw water down through a course gravel bed and out bulkheads distributed evenly across the bottom of the tank and deliver water to the aforementioned sump.  In previous dialogue, you encouraged me to avoid using UG filters and guided me towards a sand bottom.  Many hours spent mulling through your FAQs helped me clearly understand the logic of your recommendation and convinced me a redesign was in order.
Redesign #1:
Your recommendation to use a DSB now seems like the optimal choice.   
The height of my tank (45") leaves plenty of room for the DSB.  I still wanted to incorporate the principle of drawing unfiltered water from the bottom of the tank, so I repositioned the location of the bulkheads from the center of the tank to back perimeter.  I designed a simple acrylic box structure (full length of tank, 5"W, 4"H) that will rest on the bottom of the tank, butted up against the back wall and resting over the (4) 1.5" bulkheads.  A small 1/8" opening runs along the full length of this chamber and protrudes above the DSB to draw water across the DSB, down into the chamber, out the bulkheads and up into the adjacent sump.  Bulkhead location in the bottom of the tank seemed optimal because it would ultimately suck out any detritus that settled into the chamber.  Keeping the chamber to the rear of the tank drove the requirement of locating the bulkheads as close to the edge of the
tank as possible.
Today's dialogue has again exposed flaws in my design. Drilling through a 1/2" bottom plate will push the limits of a marginal design. Anything short of full, stable support for a tank weighing 7,000 lbs, resting on a 1/2" sheet of acrylic is unwise at best - plumbing underneath is out.
<Yes>
Redesign #2
Where do I go from here?  I would still like to draw water from the bottom of the tank.  I would like to maintain a very clean tank interior (no visible bulkheads, stand pipes, etc).  I could keep this chamber concept alive by simply shifting the bulkheads to the rear wall (as you suggested) but my objectives above would require me to drill holes for the bulkheads leaving only 2" of material from the bottom edge of the sheet.  1" thick acrylic makes this less of a concern than the 1/2" sheet, but is it still to be avoided?
<If practical. You could run plumbing for the main tank intake inside the system... with just one pipe (that you'd have to prime and cap... coming up, over the wall of the in-tank sump... But I encourage you to consider yet another possibility... of using space behind the tank for a much larger sump... having the water exit from thru-hulls in the sump area (if you'd like) with overflow and near-bottom draw of water to the sump from the tank... and batch processing, treating the water in the external sump... the internal one is going to be too much trouble (1' width is a pain to get in/out of as you'll see) and the circulation you'll want will be too much to draw in and move through it.>
Is the concept of drawing water from the base of the tank to maximize the removal of waste and detritus valid?
<Yes... but dependent on many other factors>
Does my design concept of using a chamber buried within the DSB to unobtrusively draw water to the sump have a chance?
<Not IME>
I am open to rethinking the whole water flow design concept and would gladly leverage any learning's from your training and experience.  Of course, the tank itself (dimensions, material thickness, sump) offers little flexibility for change as it is essentially complete (small consolation - no holes drilled yet).
<I see>
I obviously should have done more homework before I started this project - I thought I knew more than I did.  Spending 10 years in the
marine hobby from 1976-1986, with 5 years working for a LFS, helped me learn a lot, but that education seems to be about as useful today as my
father's slide rule.  "My how things have changed".
<Yes>
I've learned a tremendous amount over the past month, thanks to your website and all of the resources present, not the least of which has been your personal council. I've read Paletta's book and have yours on order. I'm playing 'catch-up', and intend to learn a lot more before this aquarium is officially launched.
<You'll do fine>
Again, thanks for your ear and for your guidance to date.
Regards,
Steve
<I wish you lived close/r to San Diego... we have a hobbyist club here with folks that have large systems as yours... who have gone through similar approaches, trials... You could simply visit with them, see what they have done. I would abandon the current design, and add a large external sump (like 200 gallons... like a polyethylene tote...) and likely drill the tank, attach street elbows to the bulkheads (to adjust overflow of the main tank height... and do some dreaming, scheming re pump choices... Bob Fenner>

Re: My Acrylic Aquarium
Bob,
Again, thanks for the advice.  Living in San Diego certainly has its appeal - its a bit warmer than Minneapolis this time of year.....
<Brrrrr~>
An additional external sump makes sense (fed from the small sump attached to the main tank).  I also like the idea of feeding water from the main tank directly to the small sump through the dividing wall (surface overflow and near bottom draws). At this point, you've got me convinced to get rid of external plumbing all together, if possible.
<Ah, good>
Is there any benefit to drawing water from near bottom on both ends of the tank (accomplished by running a piece or two of 1.5" PVC under the
DSB from the far end of the tank into the small sump), or is drawing from only one end of the tank adequate (nine feet seems like a long
ways to pull from only one end).
<Better to not complicate things here... with sufficient water movement no worries re detritus accumulation. Do take a read through WWM's marine plumbing areas... starting here: http://www.wetwebmedia.com/pbfaqsmar.htm and on for much more input on possibilities. Bob Fenner>
Thanks and regards,
Steve

Re: My Acrylic Aquarium
Bob,
Thank you for your time and helpful advice.  This is a great website and a tremendous resource for the hobby.   
<Glad we have found each other>
I'm off to read up on plumbing, sump design,.....
<Ah, good. Bob Fenner>
Steve

Re: diy acrylic aquarium
Thanks Bob for the quick response re. my 72"x20"x24" acrylic thickness but it brought up more questions.
First, does it matter if the sides "frame" the bottom panel or can they sit on top of it?
<Better to build the sides, front and back on the bottom>
If they can sit on top, why does the thickness of the bottom piece matter if it will be totally supported as acrylic tanks should be) by the stand?
<Mmm, helps to resist shearing force... by uneven support underneath (the stand, what it in turn sits on)... the most force is actually on the bottom>
Does thinner material (3/8" vs. 1/2") "stretch"?
<Yes, to a small extent more>
I've already got the material and am trying to avoid spending any more $$ unless I HAVE to? My wife is rooting for no more material, but I think she will be much more upset if 150g hits the floor! Thanks again, Scott
<Agreed... if you haven't cut the sheet and the paper is still on it, ask the supplier to allow you to trade it in for 1/2"... This is what I would do. Bob Fenner>

Re: diy acrylic aquarium
One last question...for now. Do you know if it would be possible to purchase 1/4" acrylic and solvent bond it to the 3/8" to "create" a 5/8" thick piece for the bottom (as an alternative if the acrylic guy won't exchange 3/8" for 1/2") Or am I grasping at straws that don't exist!
<The latter. Bob Fenner>

Re: diy acrylic aquarium
I am making my own 72"x20"x24"h acrylic tank. I am using 3/8" for the bottom and 1/2" for the sides.
<I would make the bottom (and top, see below) at least 1/2">
I am planning on two 1 1/2" overflows that will be located in a 5"x20" overflow box built into one end as this tank is sitting on a partition wall and will be viewed from the other three sides. First, will these overflows be sufficient if/when I gradually progress to hard corals?
<should be, yes>
Second, I was planning on using 3/8"x3" strips of acrylic to make a rim around the top of the tank with three 3/8"x5" strips used as bulkhead
braces (front to back) spaced evenly.
<I would make the top one piece, route out the openings for access>
Will these "strips" be sufficient to reduce bowing or should I get a solid piece of 3/8" and make cutouts as is
commonly done? And is 3/8" thick enough for the top?
<Make the top, bottom, at least as thick as the sides, front/back. Bob Fenner>

How thick is thick enough? (custom tank construction)
Hi, I have read hours of great ...GREAT info on this site!. I am building My own tank and I plan to start next week. It will be plywood and acrylic (Plexiglas) the dimensions I would like to build will be 96" long x 24" deep x 48" Tall, I have priced all of the items to include the very hefty 1" thick sheet of Plexiglas.... BUT?? will 1 inch of thickness be ok? also will 1" thick plywood be enough? The rest I can Handle through the outstanding idea's and instructions in your site, Thank you very much, Sincerely, Michael Waszak
<Mmm, well... if this tank's viewing panel were braced all the way around it would do, but likely bow too much (to suit me)... I would increase the thickness of the plexi and paneling if it will fit your budget. Bob Fenner>

Re: How thick is thick enough?
Thanks bob, I have decided to change the tank size to officially, 96x18x48.   with the 4x8 foot plexi @ 1" thick. do you believe that the glass and 1 inch plywood wood with these dimensions would cut down on the bowing?
<These are the same dimensions as listed before (for the building materials)... the width (L X W X H) is not important here... the depth is. The "answer/response" is the same)>
( the master plan here is really a compromise, My wife Loves LONG! and I've always wanted a tall tank....) She plans on lots of smaller schooling fish. fish turning wouldn't be an issue (depth)......another question i guess would be should I drop down to 96X12x48? i really appreciate the time you give to help people like myself. I will send you a finished pic or 10 :-) oh yeah..It will be braced all the way around!
<I think we/I am confused here... the middle dimension you list is the height? You can easily have this tank three feet (36" in height made of these materials with little detectable bowing, risk of structural failure. Bob Fenner>
WHAT WE ALREADY DISCUSSED~
Hi, I have read hours of great ...GREAT info on this site!. I am building My own tank and I plan to start next week. It will be plywood and acrylic (Plexiglas) the dimensions I would like to build will be 96" long x 24" deep x 48" Tall, I have priced all of the items to include the very hefty 1" thick sheet of Plexiglas.... BUT?? will 1 inch of thickness be ok? also will 1" thick plywood be enough? The rest I can Handle through the outstanding idea's and instructions in your site, Thank you very much, Sincerely, Michael Waszak
<Mmm, well... if this tank's viewing panel were braced all the way around it would do, but likely bow too much (to suit me)... I would increase the thickness of the plexi and paneling if it will fit your budget. Bob Fenner>

Sump Baffles
Hi All,
<Hello>
I have a sump question.  I read an old FAQ about an acrylic sump a guy was making and he wanted to attach a few acrylic baffles in it.  Bob mentioned that as long as they are not structural, you can avoid using the Weld-on product and just use silicone rubber, the type you find at the hardware store.  I got some stuff from Home Depot, 100% aquarium use silicone, I assume this is what he meant?
<Yes>
Also, since I will be adding two baffles, one for the divider of the first chamber to the second which will go from the bottom up about 9 inches or so with water overflowing over the top, and another smaller one a few inches high in just in front of the bulkhead to the return pump to prevent bubbles or whatever else, I assume these are not going to be structural in any way.  They should be able to hold back the weight of the water without any problems, using only the silicone.  Is this correct?
<Correct. Give the Silicone a day to cure before filling the sump. Bob Fenner>
Thank you
Paul

Acrylic tank building
Hello to the greatest crew on earth.
<Howdy>
Couple of quick ones I hope, I am considering building my own acrylic tank.
Call it 48"L x 20"W x 24'H,( 100g ?). I was planning on 1/2" and wondered if a 3/4" x 1 1/2" solid oak frame around the top would be adequate to prevent bowing of the front/back.
<Should be>
Would you recommend any further front to back bracing?
<Yes. At least a brace front to back on the top... or better, a solid piece with holes routered out for access... solvented along the entire top edges... like production acrylic tanks>
Also I was planning on bending the front and sides from one piece, if I build a jig to secure the front could I bend the sides around a 3/4" dowel using a blow torch or would a heat gun be better?
<... careful here. I strongly encourage you to just "butt" the corners together for this system. The heating gear for doing bends is more involved... easy to ruin many sheets in experimenting. Do you live near a manufacturer, fabricator that does heat-bending? Do call, visit them first if you're still interested in pursuing bent corners>
I built my own 30g sump with 3/8 as well as my own overflow box with good success so I think I'm up for the challenge, any suggestions or pitfalls to look out for?
<Mmm, many... make sure your cuts are square, clean... maybe use more viscous (thicker) solvent...>
Also was planning two 1 1/2" overflows in back corners, would this be adequate for a 40 gallon sump.  I figured this would give me about 1400 gph?
<Okay>
As always your kind help is very much appreciated.
<Have you considered making such tanks for others? I sense a pet-fish entrepreneur here. Bob Fenner>

A Small Set-Back (catastrophic tank failure)
Hello, Bob.
Thought I'd share this evening's adventure with you and your readers.  
My project of the past 6 months suffered a slight set-back this evening.  In the process of filling my 112Lx38Wx45H aquarium with water for it's second wet test, it suffered a catastrophic failure.  When the water was about 4" from the top, I heard the dreaded sound of a very deep thud (sounded like ice cracking on a Minnesota lake during the spring thaw).  Upon hearing the thud, I knew immediately the tank had failed and I quickly turned off the water.  Within a few seconds the entire front 1" sheet of acrylic gave way and my surprised wife (who was down the hall) later described the tidal wave of 800 gallons of water approaching her with a certain amount of disbelief.  
<Oh no!>
I've spent the last several hours wet-vac' ing the carpet in the basement - probably getting up around 100 gallons.  The rest will wait until tomorrow morning for professionals to come with industrial sized vacs and fans to finish the job.  
<Money well spent>
Three flooded bedrooms and a flooded family room all have very soggy carpeting. Storage rooms have lots of soggy boxes.  The aquarium room has holes in the dry-wall where the 6'x4' chunk of broken 1" acrylic was swept 9' across the room and into the opposite wall.  The 9' ceiling is wet where the water hit the wall and splashed upwards.  The dislodged acrylic broke a leg on a 6' ladder that was in its path as well as crushing a metal chair.  I am grateful that my kids were not in the room watching at the time - injuries would have been likely.
<Have seen damage from such breaking tanks. Agreed>
The top failed at almost exactly the mid-point of the middle cut-out (not at a corner) which leads me to believe the front face actually failed first.  I measured almost 3/4" of deflection on the front pane during the first wet test.
<...>
On the positive side, the aquarium failed during a test run with clean tap water.  It could have failed somewhere down the road with 800 gallons of salt water, 1,000 lbs of aragonite sand, and with significant live stock in tow.  I choose to be thankful for the circumstances of today.
<You are wise here>
I'm off to bed.  Tomorrow is going to be a busy day........
Regards,
Steve Walker
<Will you rebuild this tank with thicker material... or perhaps "cut down the height with the 1"? Bob Fenner>

Starting Over (800 gallon acrylic)
Hello Bob and WWM crew,
<Hello Steve>
Following the failure of my 800 gallon aquarium two nights ago, clean- up is well underway.  Carpet has been pulled up, padding thrown out, baseboards removed, industrial sized fans everywhere, industrial sized de-humidifiers humming away.  It sounds a bit like the continuous drone of a jet engine in our house.
<Thank goodness no one was injured>
The cleaning service I hired suggested I was fortunate things are not worse and estimated that this will be a relatively quick clean-up that shouldn't take more than 7-10 days of aggressive blowing/dehumidifying to complete. I'd hate to be 'unfortunate' in this situation.
<Have seen, been part of some of these cases>
While much work remains to simply get back to the place where I started this project (not the least of which is carving up the remains of the
old 1000+ lb aquarium and hauling it away), my mind is moving towards thoughts of starting over.  
<Good>
My aquarium manufacturer is re-grouping and is preparing their plan for a second attempt at this aquarium.  I intend to be a bit more involved in the selection of materials on this go-round.  Your thoughts would be greatly appreciated here (and I fully understand that your thoughts do not constitute an engineering recommendation and should not be relied upon as such).
<Okay>
It is my desire to maintain the original design specifications (112Lx38Wx45H). The price of acrylic seems to rise exponentially as thickness increases beyond 1".
<Yes. It does>
I believe I will find a way to fund the leap to 1.25", but this will likely be my limit and may need to adjust my design accordingly.
<Okay. A comment re the cost of acrylic sheet... There is a "strata" of manufacturers, distributors, dealers... and fabricators can fit in most anywhere in this scheme... What I am trying to say is it pays to "shop around" for the materials here... There is a HUGE range of costs/pricing...>
If I hold to the plan of 45" height, have you observed aquariums with these approximate dimensions constructed with 1.25" acrylic that seemed structurally and visually sound?  
<On this run (length) of tank, the tallest I would go with one and a quarter material is forty inches... really. AND I would make the rest of the tank out of the same thickness... including the top and bottom of course>
If you would be willing to offer an opinion, I will further ask what you would consider to be the maximum height for 1.25" acrylic and 1.0" acrylic, respectively (while maintaining a healthy safety margin and acceptable visual appeal)?  
<There are a few stipulations (set on a flat, planar, level, strong stand... and that the cuts are clean, square... and the solventing done "appropriately"... and there is a factor for the length of the system... but all this taken into consideration, 36" height for 1" material all the way around... and forty inches for 1.25"... and for four feet of height... 1.5"...>
No worries if you prefer not to speculate on these questions.
<These are not speculations... our companies fabricated acrylic aquariums for several years (fourteen if memory serves)... and... yes, we tended to be overly conservative... as many of our sales and installs were in California (where the ground shakes considerably at times)... or sold to "unknowns" that might have not done quite as conscientious a job in some way/s that might compromise the structural integrity of our tanks...>
  I understand they are better suited for the manufacturer - but nothing beats the opinion of an experienced and trusted aquarium fabricator.
<Agreed>
Thank you again for your valuable website and for your willingness to provide capable assistance.
I remain gratefully yours,
Steve
<A pleasure to share, learn. Bob Fenner>

Re: Starting Over -
Bob,
<Howdy, Bob is in Brooklyn giving a pitch, today you get JasonC instead...>
Thanks very much for your candid advice on acrylic thickness for my large aquarium re-design. <Indeed, what a story.>  
Given the recent catastrophic failure of my 800 gallon aquarium, my tolerance for risk is gone. <I don't blame you.> A conservative design with an ample margin of safety is the only approach that will suffice - not only for my own well-being, but for my wife's as well - recognizing that I need to regain her trust and support before I can, in good conscience, move forward with another attempt. <I hear that.>
Negotiations still remain with my aquarium fabricator regarding the losses I have incurred, but hope to quickly put that behind me and focus my energies on plans for a (safe) 40" high aquarium using 1.25" acrylic. <Do consider building in a margin of safety, either go with thicker material at that height, or lower the height - just to add to the fault tolerance.>
Until that time, I hope to make good use of my second chance at designing my system.  More reading, dreaming, planning. <Sounds good.>  
Best regards and deepest thanks,
Steve
<Cheers, J -- >

-Starting Over - Large Acrylic Aquarium Design
Hello Bob,
In our last correspondence, you recommended a thorough search of acrylic suppliers to find the most reasonable price for 1+ inch acrylic.  I was amazed at what I found.  1 and 1/4 inch stock varied in price from $570 to $960 for 4ft by 8ft stock.  Do you believe the quality of the materials offered varies enough to account for (or contribute to) these price differences?  
<Not likely. More a matter of price differences due to lack of competition>
I have modified my design/expectations to accept a shorter run length of 8 ft, instead of the 10 ft used in my original (failed) design.  I intend to use 1 and 1/4 inch material everywhere.  My design is intended to maximize volume with available 4'x8' sheet stock - 96"L x 48"W (possibly a bit narrower) x 40"H.  My question is as follows:  If 40" is the maximum safe height for this material, does the 40" limit represent the true height of the water column, or the combined height of base + walls + top?
Put another way, if I use 1 and 1/4 inch base and top, are 40" Walls acceptable (resulting in total tank height of 42.5")?  
<Yes, this last>
Thanks again for your assistance.
Best regards,
<Bob Fenner>
Steve

Acrylic questions
Bob,
A couple of questions for you regarding acrylic and its use in sump/tank construction:
1) What type/brand of acrylic would you recommend for aquarium construction.
There are many types: Plexiglas, Acrylite, Optix, etc, and I'm not sure which one (if any of these) are appropriate for aquariums (i.e.. transmit PAR light, maintain rigidity-avoid warping, avoid discoloration, etc).
<Hmm, actually most acrylics are pretty much the same. What people call them are more brand names then different formulations. I am a big fan of Reynolds as a manufacturer...>
2) What type of acrylic cement is best for capillary bonding acrylic in aquariums (Weld-on#3 ?).
<Weld-on for sure... Number three is okay... look for/use a "gel" type if this is one of your first tries at making acrylic anything>
3) What type of acrylic would you recommend for filtering UV while allowing other light to transmit freely (esp. PAR).
<Again, just whatever type you can find that is reasonably inexpensive of about the right thickness. I would not transmit "useful" light through the acrylic... shine it directly into the water>
Lastly, I've found a fluidized bed filter used in the shrimp aquaculture industry that's rated at handling 2 lbs of shrimp feed per day. Any guess at how much raw live rock this filter could handle if I used it in the curing process - along with heavy skimming (i.e.. skimmer output set to 5 times the number of gallons of water, with 1 gallon of water per lb of Fiji rock in the curing tank).
<A guess is "a bunch"... Shrimp are very dirty animals to culture... I'd guess if the folks who engineered this are saying "two pounds of shrimp feed", this equates to hundreds of pounds of live rock. Really. Bob Fenner>
Thanks!

Acrylic
Real quick. With acrylic to glass contact, the 100% silicone I have read about in the F&Q's will work right?
<I wouldn't trust it for aquaria... but for little troughs/trays/filters...maybe>
And definitely for acrylic to acrylic. 
<do use proper acrylic glue for this>
About cutting acrylic for bulkhead fittings. I have hole cutters for doors and such. this will work fine,
<yes if sharp>
and put the silicone on either side of the bulkhead and let stand 24 hrs. 
<OK... but neoprene gaskets that come with many bulkheads compress nicely and are more reliable>
Great job guys, Bryan.
<thank you kindly, Anthony>

DIY info
Hello
<Cheers.. Anthony>
Do you know were I can get some info. on building a acrylic self-contained tank with a sump and skimmer all in one. Thanks for your help and your time. Frank Thomashefsky
<many places on the Web... please try the DIY link on www.ozreef.org best regards, Anthony Calfo>

Aquarium manufacture
Bob, 
I live in Australia now and I noticed that all the aquariums for sale here are glass. I am wondering how hard it would be to set up a small facility to manufacture acrylic aquariums. 
<Not hard. A few thousands of dollars on the low end to a few tens of thousands for more serious investment, production>
Do you know much about the manufacture of aquariums or do you know anyone that I could contact by e-mail who might know? 
<We used to fabricate up to two inch thick acrylic tanks. Have several friends in the trade who do this>
I need information on how the front piece is bent, jigs and fixtures for manufacture, on exactly the type of plastic used (do they use regular acrylic or is it coated to be scratch resistant?),
<Not coated... some "brands", makes are a bit more scratch resistant, none totally>
the thickness of plastic for various sized aquariums etc.. Do you think it would be possible to set up a manufacturing facility? 
<Possible, sure>
I think that it would be too expensive to import the tanks because they take up so much space, and the Australian dollar is very low so anything from the USA is too expensive. 
<I do understand this. We're headed that way for a few weeks next month. Land, food, diving... a bargain>>
I like the pictures that you send out every day.
<Ah, am glad to hear> 
Good luck, Mike Sweet
<Mike, a very good idea for you to investigate, invest your time if serious at this point. Here on the West coast of the U.S. or the U.K... (where friends are who will help), to learn first-hand what is involved. Let us keep talking this over. Bob Fenner>

Aquarium manufacture
Dear Bob,
I knew you a long time ago at the fish club in San Diego. Currently I live in Australia. 
<Ah yes, you lucky pug. Which part?>
I have noticed that most of the aquariums for sale there are glass and look like they were made in someone's back yard. I was wondering how hard (and expensive) it would be to set up a small facility to build acrylic aquariums. 
<Not too hard... considering/stipulated you can secure the sheet, solvent to meld... and relatively simple tools (for a small volume of business) like a table saw, blades for cutting plastic, clamps, propane burners for burnishing...>
Most of the small aquariums for sale in the USA have bent corners instead of glued corners. Is that for looks or for some other reason?
<Mainly looks... (though time to make tanks reduced, a bit stronger... like castle keeps.) heat-bending is simple once you have the heating gear, jigs made up, timing down...>
I think that it would be too expensive to import aquariums to Australia from the USA due to the low value of the Oz dollar.
<How about the cost of acrylic itself...? And is there some sort of market currently, one you could hope to create... within a few years?>
Do you know anyone I could contact about this subject? I will be in the USA until December 29.
<A bunch of folks... who would likely help you themselves. Please contact Craig DeWalt of CASCO/SeaClear: c_dewalt@seaclear.com, check out their site, www.seaclear.com on the net re your wishes, visit. We are old friends/associates... make that middle-aged ones, so please do mention my name.>
Are you still living in Mira Mesa? 
<Yes... moved a whole couple of miles to the north recently... sigh. But we're hauling down to the "land down under" this March...>
I was in Fiji two years ago and went out diving with Walt Smiths' collectors a lot. They were very friendly to me. I heard that you came out to give a talk. 
<Yes, folks so nice they put up with even me...>
Unfortunately, I couldn't attend. I hope that all is going well with you. I like your
web site. 
<Hope to dive with you soon! Bob Fenner>
Mike Sweet

Acrylic Thickness
Are there any guidelines to follow when building an acrylic aquarium or for a 90H measurements of 48x18x24 what would be the acrylic thickness needed? Thanks
<Yes... some for structural strength... at least 3/8" (with an annealed top that serves as a brace), better 1/2" for the sake of cutting down of deflection/bowing. Bob Fenner>

Acrylic Thickness
I am looking into building an Acrylic Aquarium with the following dimensions: L=48" X W=24" X H=20" which will have a capacity of 100G. What would be the thinnest Acrylic I could use?
<1/2" with a capture/top piece.>
I would like to use 3/8" (.375 in) if possible as I can get a good price on 48"X48" sheets. Gregory A. Maher
<I would build a smaller tank. Something in the 36" long, 30 gallon range. -Steven Pro>
<<RMF thinks the 3/8" would be fine here... used for this height tanks in the industry>>

Most Everything You Ever Wanted To Ask/Know About Acrylic Aquariums
Dear Bob, I have tried to put all my questions in one list. Can you help me with any of these? Thanks for your help. Mike
<<Greetings, Mike. JasonC here, and I will do my best... >>
1) What thickness of acrylic is used for 20 gallon, 50 gallon and 100 gallon tanks? 
<<Well... the answer depends on the actual dimensions of the tank. On a general rule of thumb, perhaps 3/8" for a 20 up to 1/2" for the 100 - if there were one long panel, perhaps 5/8" or up to 3/4" for larger tanks. Probably best to break out the calculator and the acrylic manufacturer's spec sheet and do some homework.>>
2) Are the top, bottom and sides of the tank all the same thickness?
<<Again, this depends on the desired dimensions of the tank. The safe assumption is that IF you are making a perfect cube, all walls can be the same thickness. If you start stretching the cube into a rectangle, then the assumption changes.>>
3) Do they use regular acrylic glue or a special glue?
<<As far as I know, it's a standard acrylic glue - creates a molecular bond.>>
4) Are the corners bent to a different radius for different size tanks?
<<Corners are bent to a different radius for different thicknesses of material and visibility.>>
5) Can a small tank be made that has glued corners instead of bent corners? <<Sure.>> 
Why are bent corners usually sold? 
<<Easier than jigging up and adhering four walls with perfect 90 degree joints.>>
5.5) What is the radius of the bend of 20, 50, and 100 gallon tanks?
<<Depends on the material.>> 
6) Is the radius of the bend for strength or for looks?
<<Both... the material would maintain is strength for a while beyond a bend that ceases to look clear.>> 
7) Is the acrylic bent on a specialized machine or is it heated with a local heating element and bent over a mold?
<<Depends on the application. On smaller panels, I have seen a blow torch used. On larger, curved aquariums a large walk-in oven is used.>>
8) Can the acrylic be trimmed to fit after it is bent or does it have to be bent perfectly?
<<Well... the whole job has to be done perfectly. Cuts, joints, bends, you don't really get a second chance on the same piece of material.>>
9) Is it very hard to bend acrylic over a mold and get a perfect bend?
<<Let's just say that it is a skill, and one that can be learned. But not so simple that you'd get it on the first try.>>
10) Are there any special tricks that you know that help in bending the front piece of acrylic? 
<<Patience, lots of patience, that and a fairly exacting eye for detail.>>
11) After the front piece is bent, are there any special difficulties gluing on the top, back and bottom? 
<<Well, you want the thing to hold water... it's not as easy as it might seem.>> What order is best? 
<<Probably front to the back, and then that assembled piece to the bottom.>>
12) Have you heard of someone setting up a small shop to make acrylic aquariums? 
<<Uhh... Jason Kim of Aqua C comes to mind. He makes a fine line of protein skimmers, but also makes custom tanks and sumps. If I'm not mistaken, he started out as a one man operation. His skimmers are quite popular, and so he's not a one-man-show any more.>>
13) What fraction of aquariums sold in the US are acrylic now?
<<Couldn't tell you... but a quick mental survey says: depends where you live. If you live in an earthquake zone, you might not have a choice. Acrylic tanks are more expensive than their glass cousins so income plays a factor.>>
14) What is the difference in wholesale price of glass and acrylic aquariums in the US? What is the difference between the internet price and the wholesale price? 
<<I really don't have that information. You'd do best to ask the actual wholesalers and retailers.>>
14) What are the major advantages of acrylic? 
<<Two come to mind... acrylic is a better insulator. That and it is also much more clear than glass tanks which become more green as the glass gets thicker.>>
 Disadvantages? 
<<There are three disadvantages. One, price - acrylic tanks are much more expensive than glass tanks of the same size. Two, acrylic is easy to scratch and it's easy to do with a large chunk of live rock. This also means you need special cleaning pads. Third, and if you keep a reef tank, coralline algae has a strong attraction to plastics, acrylics included. This means that you either need to clean the viewing panels constantly, or go after them with special scrapers when you can't see the inhabitants any more like I do ;-) >>
15) Approximately how many manufacturers of 20-100 gal stock acrylic aquariums are there in the USA: 5, 10, 25? 
<<That's a good question, but I just don't know the market that well. I'd bet there are more than five, but not 25. Maybe more than 10 but not many more. Just a guess though.>>
16) Is it better to use a router, table saw or a panel saw to cut the acrylic?
<<A precision table saw with special blades for cuts. Router for cleaning the edges. Hope that helps. Cheers, J -- >>

Building an acrylic aquarium I was wondering if you could help me with a few questions. I am thinking about building an aquarium about 55 gal or so and I have read many articles about what thickness of acrylic to use for what height aquarium and so forth. I was wondering if you could use thinner acrylic if you were to frame the tank with a plywood box. (please see attached drawing)  <Not really... the thickness should be about the same or the same per height... If this is a "typical" 55 of 22" height (or even twenty inches), I would opt for a minimum of 3/8 inch (even half if you can afford it)... the bracing may well help to prevent bowing, even breaking... but the mid front and back will bow badly and result in noisome distortion if you try 1/4... or yikes, less thickness> For example, could you use 1/4" acrylic on a 24" high tank in this manner. I have also read about the wood and glass tanks but I would like to keep at least 3 viewing sides open. The wood I could get free and the 1/4" acrylic costs significantly less than the 1/2" so I figured I'd ask someone else what they thought before I flooded my garage. If it is possible to do this how substantial do you think the frame would have to be? Thickness of the wood 5/8 or 3/4? <Not really practical here... though I have made many (hundreds years back) of glass fronted (and you could make cut-outs for the sides as well) and plywood, resin and fiberglass (stripping is best here, pre-made and available in rolls) tanks... with 3/4 and 1" ply and good brass screws (2 1/2 or three inch)> and how much of the viewing area would I have to cover? <For the glass et al. structures, a good three or four inch edge is good all the way around> Would it be a good idea to pad the inside of such a frame and to give it rounded edges? If it did work it would then be very easy to incorporate a nice wooden hood. Thanks for you time, Great website! Christopher C. Hehn <I like the way your mind and writing presents it/themselves... do keep investigating. Maybe Oz' Reef: http://www.ozreef.org/ Great, one-stop DIY site for pet-fish types. Bob Fenner>

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>

DIY Acrylic Tanks
Hi this is Abraham, my first time here. I'm looking to utilize acrylic sheets for marine fish holding systems. My question is how do you cement the sheets together, meaning which material is aquarium safe? In addition, which silicone sealant is aquarium safe? One more question, how do you figure the thickness needed of the acrylic sheets needed for reservoirs for the sump tanks? I understand that it depends on how much water is being held in one given place. So for instance, a holding system of 8 feet long by 2 feet wide and making several of these units tiered one above the other in relatively shallow pools, no more than a foot high. For example; what thickness of acrylic sheets is minimally needed. Understandably braces are needed on top as well. Please try to help me out with this as soon as you guys can. Thank you and I am gratefully appreciative of your time and efforts.
<Please begin here http://www.wetwebmedia.com/diytksfaqs.htm and follow on through the related FAQ files for the answers to your questions. You can also use the Google search engine at the bottom of each page to help you locate topics quickly. -Steven Pro>

Acrylic Wall Thickness for Large Tank 7/17/04
I am building a very large tank in the shape of an equilateral triangle.  The dimensions are 24 feet long by 8 feet to the point of the triangle by 4 feet high (or deep).  It will be placed on a strong 18 inch concrete floor.  I am guessing that 2" for the sides and 1 inch for the top and bottom should hold well but I am just basing that on my limited engineering experience.  Do you know how I could find out if these dimensions will be OK.  Can you recommend any structural engineers if I need one or is it not that complicated if I know how to figure it out.  Thanks Dimitrios
<Hi Dimitrios!  I hope when you say that you are building this tank, that you mean you are having it built.  This is not a DIY project!  I would begin by contacting some of the following:  A large public aquarium, Reynolds Polymer and San Diego Plastics.  I would consult a structural engineer about the floor.  A public aquarium should be able to direct you to large tank manufacturer (SD Plastics is one, but this project may be beyond even their capabilities).  Reynolds polymer makes very large, very thick acrylic material for public aquariums.  They can probably direct you to a manufacturer that deals in large display tanks.  There are wall thickness calculators on the 'net for acrylic tanks, but they only apply to rectangular tanks.  Good luck!  Adam>