500g Reef Tank Build Saga: A Guide on What Not to Do
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Following along! She really was a beauty before she dumped her water!
Tl02022020
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updates? Working on covid testing is a pretty good excuse I guess....but we need the next installment! 
Kidding of course! It sounds like what you are doing at work is super important. But when you feel like sharing some more of the tank journey, we are anxiously awaiting it!
Kidding of course! It sounds like what you are doing at work is super important. But when you feel like sharing some more of the tank journey, we are anxiously awaiting it!
h2so4hurts
Active Member
Last post ended with a picture of my newly built lagoon. Unfortunately that wasn't by choice and was the result of some questionable building decisions on my part.
The night it started leaking I was doing a bit of tank maintenance. It'd been about 3 days since I filled an scaped it and there was some algae starting to grow along the window edges. I did some scraping, moved some of the sand around, and then went back to work behind the tank tidying up the wiring. While back in the fish closet (can't really consider it a room) my wife asked me if there was supposed to be water on the bottom edge of the tank. At first I didn't think much about it. I must have just splashed some water out while scraping so I wiped it up and went back to what I was doing only to see the water reappear after about 15 minutes. That was a pretty clear indication there was a small leak. But I couldn't see it, or feel it, because with the top bracing the tank was 39" tall. I do not recommend a 39" tall tank... I drained a little water out and bent over the edge of the tank so I could fit my body in there and still couldn't see or feel the bottom seam of the acrylic. So I decided to get into the tank...there are pictures, I'm not posting them.
I finally felt where the seam was and apparently I hit the bottom edge of the seam with my scraper, it pulled away because 3M 5200 does not stick to acrylic basically at all, and then water squeezed out slowly through the seam. Just touching the seam that had pulled away made it pull back more which made the leak worse until basically the entire bead of 3M 5200 pulled away from the bottom edge of the front of the tank. The leak got progressively worse, I tried squirting more 3M 5200 along the edge to see if it'd get pulled into the leaky spots and that did nothing so I made the executive decision to cut my losses and empty the tank to try to see how I might be able to fix the seam and salvage the build.
I spent about a week trying every marine adhesive known to man to fix the tank seam. I got really familiar with my sander, putty knife, and dremel oscillating head tool. So, just so everyone knows, 3M 5200, 3M 5200 fast cure, and 3M 4200 do not bond with any strength to acrylic. It peels off, even after roughing up the acrylic with 60 grit sand paper, and it peels off with minimal force.
I then got the bright idea to try to fix the tank by making it look more like a commercial aquarium where the acrylic pane is held in place by a metal frame that's through bolted to the sealing surface and covered in marine adhesive to prevent the metal or the bolts from rusting. I had a local fabricator weld up the frame.
I then got a drill guide and drilled about 60 holes...
We through bolted, covered everything in 3M 5200, and torqued the bolts to 3 ft/lbs
I let the 3M 5200 cure for a week before I went ahead with a week long water test.
And it held water perfectly for a week. I was pretty excited that I had solved the problem until I went into the tank to take a look at the seam. It all looked great, until I started drying the seam. When I pushed on it, it looked like it was sweating. The 3M quick cure had little micro bubbles in it, or something, and they burst under the water pressure and filled with water. This happened on a handful of the bolt heads too, exposing the metal directly to the water. At this point I wasn't going to chance it. I had added and removed marine adhesive more times than I could count and it was obvious to me that the tank was going to have questionable longevity. I made the decision to demo it and pursue a different route.
By this point it was the middle of December. The goal was to have everything tidied up by Thanksgiving, so, easily a month overdue with about 3 months of work devoted to the build prior to filling it with water. Not to mention the $3500 of materials that went into attempting to make the tank. It was a big decision to cut the cord, but I knew that if I put everything back in there I would always worry about it leaking or rusting internally, neither of which would have been a desirable outcome. So I asked a bunch of friends from work to come over again and take down the tank so I could cut it a part and start over.
Tank's Down
Friend helping rip out the frame and bolts, 3M 5200 sticks to stainless steel really well, unfortunately...
Ending with everything all piled up on the driveway (it's still there, by the way, because I want to cut out the acrylic windows and salvage them for another project).
Now that the tank was down and disassembled I was able to do a post-mortem. For starters, the sealing edge I had on the tank was not adequate. 1.5" of frame is not enough to account for bending of the acrylic under stress. A minimum of 4" should be used for acrylic tanks, more is better here to provide support and limit the amount of stress that is put on the acrylic and sealing seam. Another option that seems popular in commercial aquariums is to add an intermediary epoxy agent in between the acrylic and marine adhesive to facilitate bonding. I wish I had discovered this sooner, because it potentially would have been easier than drilling all of those holes. The idea here being that certain epoxies stick really well to acrylic AND to marine adhesive. Because epoxy is brittle, you can't use it in high stress areas but you can use it to bridge the acrylic to an adhesive that has much better elongation and flex tolerance. While looking at my stand, I also noticed the support on the bottom of the tank also was not adequate. I had failed to notice that when the previous tank settled it bowed the deck of the stand by about 1/8", so not only was the weight of the water bending the acrylic ever so slightly it was also bowing the bottom of the tank, which put added stress on the front bottom seam basically being pushed away by the acrylic surface and pulled down by the bow of the bottom surface. This was, unfortunately, a disaster waiting to happen and when demolishing the tank we found that the bottom plywood had already started being infiltrated by water so it's a good thing I made the decision to take it apart because it was probably about 2 weeks away from having another noticeable leak.
The sad state of my basement toward the end of December can be seen below. The next post will detail how I went about filling that massive open hole with a long term solution.
The night it started leaking I was doing a bit of tank maintenance. It'd been about 3 days since I filled an scaped it and there was some algae starting to grow along the window edges. I did some scraping, moved some of the sand around, and then went back to work behind the tank tidying up the wiring. While back in the fish closet (can't really consider it a room) my wife asked me if there was supposed to be water on the bottom edge of the tank. At first I didn't think much about it. I must have just splashed some water out while scraping so I wiped it up and went back to what I was doing only to see the water reappear after about 15 minutes. That was a pretty clear indication there was a small leak. But I couldn't see it, or feel it, because with the top bracing the tank was 39" tall. I do not recommend a 39" tall tank... I drained a little water out and bent over the edge of the tank so I could fit my body in there and still couldn't see or feel the bottom seam of the acrylic. So I decided to get into the tank...there are pictures, I'm not posting them.
I finally felt where the seam was and apparently I hit the bottom edge of the seam with my scraper, it pulled away because 3M 5200 does not stick to acrylic basically at all, and then water squeezed out slowly through the seam. Just touching the seam that had pulled away made it pull back more which made the leak worse until basically the entire bead of 3M 5200 pulled away from the bottom edge of the front of the tank. The leak got progressively worse, I tried squirting more 3M 5200 along the edge to see if it'd get pulled into the leaky spots and that did nothing so I made the executive decision to cut my losses and empty the tank to try to see how I might be able to fix the seam and salvage the build.
I spent about a week trying every marine adhesive known to man to fix the tank seam. I got really familiar with my sander, putty knife, and dremel oscillating head tool. So, just so everyone knows, 3M 5200, 3M 5200 fast cure, and 3M 4200 do not bond with any strength to acrylic. It peels off, even after roughing up the acrylic with 60 grit sand paper, and it peels off with minimal force.
I then got the bright idea to try to fix the tank by making it look more like a commercial aquarium where the acrylic pane is held in place by a metal frame that's through bolted to the sealing surface and covered in marine adhesive to prevent the metal or the bolts from rusting. I had a local fabricator weld up the frame.
I then got a drill guide and drilled about 60 holes...
We through bolted, covered everything in 3M 5200, and torqued the bolts to 3 ft/lbs
I let the 3M 5200 cure for a week before I went ahead with a week long water test.
And it held water perfectly for a week. I was pretty excited that I had solved the problem until I went into the tank to take a look at the seam. It all looked great, until I started drying the seam. When I pushed on it, it looked like it was sweating. The 3M quick cure had little micro bubbles in it, or something, and they burst under the water pressure and filled with water. This happened on a handful of the bolt heads too, exposing the metal directly to the water. At this point I wasn't going to chance it. I had added and removed marine adhesive more times than I could count and it was obvious to me that the tank was going to have questionable longevity. I made the decision to demo it and pursue a different route.
By this point it was the middle of December. The goal was to have everything tidied up by Thanksgiving, so, easily a month overdue with about 3 months of work devoted to the build prior to filling it with water. Not to mention the $3500 of materials that went into attempting to make the tank. It was a big decision to cut the cord, but I knew that if I put everything back in there I would always worry about it leaking or rusting internally, neither of which would have been a desirable outcome. So I asked a bunch of friends from work to come over again and take down the tank so I could cut it a part and start over.
Tank's Down
Friend helping rip out the frame and bolts, 3M 5200 sticks to stainless steel really well, unfortunately...
Ending with everything all piled up on the driveway (it's still there, by the way, because I want to cut out the acrylic windows and salvage them for another project).
Now that the tank was down and disassembled I was able to do a post-mortem. For starters, the sealing edge I had on the tank was not adequate. 1.5" of frame is not enough to account for bending of the acrylic under stress. A minimum of 4" should be used for acrylic tanks, more is better here to provide support and limit the amount of stress that is put on the acrylic and sealing seam. Another option that seems popular in commercial aquariums is to add an intermediary epoxy agent in between the acrylic and marine adhesive to facilitate bonding. I wish I had discovered this sooner, because it potentially would have been easier than drilling all of those holes. The idea here being that certain epoxies stick really well to acrylic AND to marine adhesive. Because epoxy is brittle, you can't use it in high stress areas but you can use it to bridge the acrylic to an adhesive that has much better elongation and flex tolerance. While looking at my stand, I also noticed the support on the bottom of the tank also was not adequate. I had failed to notice that when the previous tank settled it bowed the deck of the stand by about 1/8", so not only was the weight of the water bending the acrylic ever so slightly it was also bowing the bottom of the tank, which put added stress on the front bottom seam basically being pushed away by the acrylic surface and pulled down by the bow of the bottom surface. This was, unfortunately, a disaster waiting to happen and when demolishing the tank we found that the bottom plywood had already started being infiltrated by water so it's a good thing I made the decision to take it apart because it was probably about 2 weeks away from having another noticeable leak.
The sad state of my basement toward the end of December can be seen below. The next post will detail how I went about filling that massive open hole with a long term solution.
Last edited:
Pntbll687
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Well, if I learned one thing it is.... put off that plywood build I have in my mind until I'm absolutely certain I can do it.
@h2so4hurts , it hurts to look at the pictures, but I think this is one of the things that people don't share enough, where they failed. I have my share of failures in this hobby, and I've probably learned more from them than the successes.
If it was me I would have sold the old tank already and had nothing to put the stock back into when the tank started leaking.
@h2so4hurts , it hurts to look at the pictures, but I think this is one of the things that people don't share enough, where they failed. I have my share of failures in this hobby, and I've probably learned more from them than the successes.
If it was me I would have sold the old tank already and had nothing to put the stock back into when the tank started leaking.
nezw0001
Well-Known Member
Thanks for sharing your experience and I’m sorry!
h2so4hurts
Active Member
Use a glass window and build it on the stand you plan on using long term. You'll be good
. Just find a cheap glass supplier. I couldn't find one local and that's what sent me down the stupid path of trying to do it with Acrylic!
Tl02022020
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What an ordeal! Thanks for sharing all this, I bet it will help others.
h2so4hurts
Active Member
They have professionals do the install, not me. And the window frames are concrete, not wood.
But there is some sorta rubber seal attached to the acrylic. I dont think the tank being made out of wood or concrete makes a difference. 99% of your issue was the seal-acrylic bond. You mentioned epoxy sticks to acrylic and sealant. Cant you brush epoxy on the acrylic where the seal will occur, then the sealant will attach to the epoxy and not directly to the acrylic?
AlexG
Valuable Member
Sorry I missed this post to reply earlier. Sorry to see the end result of this tank failure but I am glad you can share this with everyone. I'll go through the initial concerns I had along with some based on your additional posts on what failed. My first concern would be the acrylic gasket seal method used. Since acrylic does not bond with silicone or RTV a gasket seal relies on pressure and very few people that use this method successfully share how they do it. Would need to know how thick the seal was and if spacers were used to maintain an even seal thickness. When the gasket seal was laid down and held in place to cure spacers would have been a critical component. I have never done a seal like this before but I would likely use a thick seal 1/16-1/4"+ thick so it could compress with the water pressure and accommodate any pressure bowing on the acrylic. Moving the tank after the seal was put in place would have been another concern as something that big and heavy will have slight movement in the structure which could compromise the seal integrity. As you mention the next concern I had would have is the stand and how it was integrated with the wall as unevenness can cause a tank to settle and again compromise the seal. This is why test filling gradually over several days is so important to weed out these issues before they compromise the tank. I had to drain my 720gal during the test fill as it started bowing and needed outside reinforcement bracing added.
The bolt method used was interesting but would rely on a even thick seal. Another option for the bolts would have been to use the stainless steel frame outside the tank to act as a washer. Then countersink the inside holes for bolt heads with washers so they would have been recessed. Then fill those counter sunk bolt holes with 5200 flush to the acrylic surface. Finally cut a small strip of acrylic to cover all holes and seal will weldon.
I never got a good look at the stand structure you had but I have 48 2x4 legs on each of my plywood tank stands. I would agree that the stand bowing would have caused an issue over time.
I agree with you as well that more of an overlap would have helped on the acrylic sealing surface. 1.5 inches is a really narrow sealing surface for a tank that tall. On my 720gal 36" tall with 3/4" glass the sealing surface overlap is 2.25 inches. I will say this does convince me not to attempt using acrylic for a plywood tank.
Thanks for sharing your lessons learned along with all the suspense between posts.
h2so4hurts
Active Member
Yep, they either have a gasket custom made or they do what I did and cover the sealing surface with polyurethane adhesive and then pressure fit the window in. I would definitely do it differently if I did it again. But I was tired of experimenting and my wife was tired of not being able to use our basement so I went in a different direction.
h2so4hurts
Active Member
Really great point. Thanks for sharing, but I think even with a thicker gasket, the sealing surface was too thin for this to work, I was getting greedy with my viewing area
Stand was reinforced and brought back to level, that'll be in the next post.
h2so4hurts
Active Member
Acrylic can probably work just fine for this, but it seems like there's a lot of extra effort when you can just slap some glass in and get a really good bond with silicon to the glass and the epoxy!Very educational. I too have been looking into plywood+acrylic for my next tank... and will follow your advice and that of @AlexG and stick with glass... thanks for being a trailblazer (in both reefs and work
First thank you for the hard work you are doing in the lab! Work like yours will get us through this faster and better.
I've just read through the entire thred and like everyone else, I was on the edge of my seat.
I'm sorry to see all the hardships you encountered on this build. I think its everyone's nightmare in this hobby which is why it's taken me so long to get my build up.
I gotta say, your old tank on the floor looks awesome all by itself
Cant wait to see what you've done after the tear down.
I've just read through the entire thred and like everyone else, I was on the edge of my seat.
I'm sorry to see all the hardships you encountered on this build. I think its everyone's nightmare in this hobby which is why it's taken me so long to get my build up.
I gotta say, your old tank on the floor looks awesome all by itself
Cant wait to see what you've done after the tear down.
I'm really sorry about your entire ordeal, but can I say, if you ever decide to pursue a career in writing, I'd be the first to buy your book! This thread is easily one of the most entertaining things I've read on this site!
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M o r e . C o n t e n t . Like the dude said above this stuff is good
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