New 300 gallon tank cracked. Couple questions please

[ozorowsky]

Hello all,

Just purchased a 300 gallon tank off Craigslist. Got it home and when I was moving the furniture dolly the bottom center cracked in 3 different directions. I can snag my finger nail on it. If I go to glass store and have them sell me some sheets of glass, and put them over the cracks and seal, should I be ok in regards to leaks? What should I adhere/seal this glass with?
Sand/ rock will cover it so not worried how looks.

There will be plywood under the tank on the stand to distribute weight, but once I seal bottom how can I leak test to be sure water isn't just seaping into the plywood?

Last question... my wife doesn't want me to build this into the wall due to worries of salt creep mold etc. But we're compromising on butting this against the wall in my dining room, cutting a viewing hole into my living room, finishing it nice with wood. What can I use to nicely and easily seal the minimal gap between the tank and where it touches wall in dining room side so kids don't drop stuff down there and stuff?

Thanks in advance

[windlasher]

Originally Posted by ozorowsky

Hello all,

Just purchased a 300 gallon tank off Craigslist. Got it home and when I was moving the furniture dolly the bottom center cracked in 3 different directions. I can snag my finger nail on it. If I go to glass store and have them sell me some sheets of glass, and put them over the cracks and seal, should I be ok in regards to leaks? What should I adhere/seal this glass with?
Sand/ rock will cover it so not worried how looks.

There will be plywood under the tank on the stand to distribute weight, but once I seal bottom how can I leak test to be sure water isn't just seaping into the plywood?

Last question... my wife doesn't want me to build this into the wall due to worries of salt creep mold etc. But we're compromising on butting this against the wall in my dining room, cutting a viewing hole into my living room, finishing it nice with wood. What can I use to nicely and easily seal the minimal gap between the tank and where it touches wall in dining room side so kids don't drop stuff down there and stuff?

Thanks in advance

Sorry to say, you would need to replace the bottom glass. In other words, Throw it away and buy a tank without cracks.

[kalare]

You may be able to purchase a whole sheet of glass, to fit perfectly inside the 4 walls, silicone it to the bottom, silicone it to the 4 sides. More or less, install a new bottom, over the other old one, that sits inside the sides instead of under it. Structurally this should work no problem (depending on what the cracks actually look like). I would match the existing glass thickness, so that you get a good thick surface for silicone. Fill it in the garage or back yard for a week or so to test it out, you should be good to go. A big bottom piece of glass for a 300g isn't going to be cheap though.

[ozorowsky]

Originally Posted by kalare

You may be able to purchase a whole sheet of glass, to fit perfectly inside the 4 walls, silicone it to the bottom, silicone it to the 4 sides. More or less, install a new bottom, over the other old one, that sits inside the sides instead of under it. Structurally this should work no problem (depending on what the cracks actually look like). I would match the existing glass thickness, so that you get a good thick surface for silicone. Fill it in the garage or back yard for a week or so to test it out, you should be good to go. A big bottom piece of glass for a 300g isn't going to be cheap though.

That's what I'm afraid of

[windlasher]

The problem (as I see it) is this. Let's assume you are going to buy a sheet that will fit perfectly over the top of your currently cracked sheet. That second (expensive) sheet is going to be heavy as hell and after coating the bottom and edges with silicone, you are going to need a way to safely lower it onto the top of the current sheet. Maybe you could stand the tank on its side and edge it in that way, but again, manipulating a sheet of glass that probably weighs at least 100+ pounds while trying not to damage the other sides, and keep it even and straight is going to be a bear. YOU will also need to essentially coat the entire bottom with rows and rows of silicone to eliminate any gaps to make sure the new sheet is perfectly aligned, flat, sealed with the old one. This might help in keeping the old one from cracking any further though.

I believe that Glass tanks are manufactured with the four sides sitting on top of the bottom. It might be easier to turn the tank over, remove the brace and cut the silicone holding the bottom piece on and replace it. Even if your bottom piece is sitting inside the four sides, it may be easier to cut it out and replace it and then replace the brace.

I'm not saying don't do it, I'm saying think and plan carefully or it could cost you even more. That second cracked piece would scare me. 300 gallons of salt water could do a lot of damage.

Good luck.

[mcgyvr]

Tank is junk now..
The whole pane needs to be replaced or find a new tank..

[JTL]

^ Totally agree. My guess is the bottom is at least 3/4" and that is going to be an expensive piece of glass. If the sides are sitting on the bottom panel it may not be too big of a job to get the old one off. Be sure to clean the side panel bottom edges to a virgin finish or you face potential adhesion issues. Also use MTV not silicone.

[billdogg]

Originally Posted by mcgyvr

Tank is junk now..
The whole pane needs to be replaced or find a new tank..

^^^This^^^

Short of a complete disassembly of all 5 pieces of glass, removal of all silicone and residue, and then reassembly, there is no proper fix. If you've never done this job before, starting on something that big is a disaster waiting to happen.

[JTL]

Originally Posted by billdogg

^^^This^^^

Short of a complete disassembly of all 5 pieces of glass, removal of all silicone and residue, and then reassembly, there is no proper fix. If you've never done this job before, starting on something that big is a disaster waiting to happen.

It may not be necessary to replace all of the panels. I have removed and replaced a singe panel albeit on a 110g tank. I agree replacing all the panes on a tank of that size should only be done by a pro. The only thing that concerns me is the weight may force out too much of the RTV.

[mcgyvr]

Originally Posted by JTL

It may not be necessary to replace all of the panels. I have removed and replaced a singe panel albeit on a 110g tank. I agree replacing all the panes on a tank of that size should only be done by a pro. The only thing that concerns me is the weight may force out too much of the RTV.

disassembly of 5 panes is not replacement of all panes..
only the cracked piece needs to be replaced

[JTL]

I meant disassembly. Obviously replacement is a new tank.

[windlasher]

Originally Posted by JTL

It may not be necessary to replace all of the panels. I have removed and replaced a singe panel albeit on a 110g tank. I agree replacing all the panes on a tank of that size should only be done by a pro. The only thing that concerns me is the weight may force out too much of the RTV.

Aquarium builders use spacers to hold the glass slightly apart and fill the seam with RTV. It is Never sitting directly on the glass. There was a very cool video by one of the tank manufacturers a while back but I don't remember who it was.

What he is saying about the five sides is that new RTV/Silicone doesn't adhere well to old. so those corners could be suspect. I once re-did a 90 without taking it completely apart by using a razor blade to score and remove all of the silicone on the inside panels and then added new to all corners. I did it because the corners were all chopped up from the razor blade glass cleaner and I wanted it to look better.


By doing it this way, I was gluing glass to glass for the most part and the stuff between the panes was still intact. I never had a problem with it and it is sitting in my office this very moment.

[ericarenee]

on a serious note.. VARY SORRY About your tank. Two options ..Tear it down comletly and replace that bottom or Replace the whole tank


Good Luck ..

[billdogg]

Originally Posted by JTL

I meant disassembly. Obviously replacement is a new tank.

New (uncured) silicone WILL NOT adhere to old silicone. I suppose that if you slopped enough new silicone over the old so that it could adhere to glass it might work, but it would look like crapola.

The ONLY proper way to repair a tank with cracked glass like the OP's (or fix any leak) is to take it all apart and start from scratch with glass that has been completely cleaned of all traces of silicone. It is a royal PIA on even a small tank. There is no way I would attempt it on a tank as large as the OP's. The risk of failure is too great. The thought of 300g of water loose in my living room would make sleep impossible.

[JTL]

Originally Posted by billdogg

New (uncured) silicone WILL NOT adhere to old silicone. I suppose that if you slopped enough new silicone over the old so that it could adhere to glass it might work, but it would look like crapola.

The ONLY proper way to repair a tank with cracked glass like the OP's (or fix any leak) is to take it all apart and start from scratch with glass that has been completely cleaned of all traces of silicone. It is a royal PIA on even a small tank. There is no way I would attempt it on a tank as large as the OP's. The risk of failure is too great. The thought of 300g of water loose in my living room would make sleep impossible.

You DO NOT have to disassemble the entire tank IF you can get the bottom panel off and clean the surfaces to a virgin state. You are correct old silicone does not adhere very well to old. The product to use is actually not silicone it is RTV adhesive, smells like silicone and has similar properties but it is much stronger. Depending on the price of the glass for the bottom I would try it, but I have built a few tanks, just nothing of this size.

[JTL]

Originally Posted by windlasher

Aquarium builders use spacers to hold the glass slightly apart and fill the seam with RTV. It is Never sitting directly on the glass. There was a very cool video by one of the tank manufacturers a while back but I don't remember who it was.

What he is saying about the five sides is that new RTV/Silicone doesn't adhere well to old. so those corners could be suspect. I once re-did a 90 without taking it completely apart by using a razor blade to score and remove all of the silicone on the inside panels and then added new to all corners. I did it because the corners were all chopped up from the razor blade glass cleaner and I wanted it to look better.


By doing it this way, I was gluing glass to glass for the most part and the stuff between the panes was still intact. I never had a problem with it and it is sitting in my office this very moment.

If the sides are not structurally defective you can clean the bottom edge and corners as you describe. I have also done that. You can usually get it clean enough to keep the water in especially if you make a wide bead. The new bottom will sit on cleaned edges.

I forgot about the spacers, but that is how it is done. I always have recessed my bottom pane so no spacers were needed on the surfaces.

[ozorowsky]

Thanks all! Online I see this bottom glass replacement for 346 shipped from admglass.com. That is also tempered glass. I guess I didn't know this was a custom built aquarium. I'm attaching pics of tank/damage. From what I'm reading here, there's hope as the bottom glass is truly on bottom. It doesn't sit inside the edges. I'm going to call glass places tomorrow see how much they would repair (properly) for. Just sucks cuz this is such an awesome tank.

[ericarenee]

Rtv is a silicone based adhesive Silicone .It has the same adhesion properties as pure silicone. It will chemically bond to cured silicone or other cured adhesives that are silicone based.. So by not tearing down the whole tank your not getting a bond on the 4 corners where the adhesive goes up the sides. The adhesive between the glass panes is what holds it together .not the adhesive build up on the corners . thou it all worked together ..

NOT Tearing the tank down completely . especially of this size is a very good way to test your home owners insurance policy ..

[ericarenee]

Originally Posted by ozorowsky

Thanks all! Online I see this bottom glass replacement for 346 shipped from admglass.com. That is also tempered glass. I guess I didn't know this was a custom built aquarium. I'm attaching pics of tank/damage. From what I'm reading here, there's hope as the bottom glass is truly on bottom. It doesn't sit inside the edges. I'm going to call glass places tomorrow see how much they would repair (properly) for. Just sucks cuz this is such an awesome tank.

so now we know why it cracked.. Very bad place to drill a tank..

[daquan44]

You can do what I did and use plywood and pond armor. It's a much cheaper option in my opinion.
https://youtu.be/_n_qNRZgFVc

I am sure I am going to get flame sprayed for saying that, but it has been holding up strong for a couple years now. It also gave me the flexibility to drill it how I wanted to.

[ericarenee]

Originally Posted by daquan44

You can do what I did and use plywood and pond armor. It's a much cheaper option in my opinion.
https://youtu.be/_n_qNRZgFVc

I am sure I am going to get flame sprayed for saying that, but it has been holding up strong for a couple years now. It also gave me the flexibility to drill it how I wanted to.

wow . maybe all tanks should have a bottom similar to this if it holds up

[kalare]

Originally Posted by daquan44

You can do what I did and use plywood and pond armor. It's a much cheaper option in my opinion.
https://youtu.be/_n_qNRZgFVc

I am sure I am going to get flame sprayed for saying that, but it has been holding up strong for a couple years now. It also gave me the flexibility to drill it how I wanted to.

No Flame from me, I was actually thinking plywood might work...and you just proved it does.

Ingenuity at its best. It's easy for all to tell you to scrap the tank when it's not their money, but I say try some cheaper fixes out and water test them...might just work out for you.

[mcgyvr]

Originally Posted by kalare

It's easy for all to tell you to scrap the tank when it's not their money, but I say try some cheaper fixes out and water test them...might just work out for you.

or it won't work out for them..
A 24 or 48 hour or whatever water test is not a guarantee that a "hack" will hold for the life of a product..
Its easy for you to say try a cheap fix when its not your house that gets ruined when the tank fails catastrophically 2 weeks or 2 years or whatever in to it either..
The damage 300 gallons of water can cause is far in excess of the cost of a new tank or a proper repair..

We say scrap the tank because thats generally the smart thing to do..

[der_wille_zur_macht]

I've seen a few glass tanks that had bottoms replaced with plywood. They'd all held up for years. If you do it right, it's a great option. I even know a few people who have built tanks from scratch incorporating both glass and wood.

I'm sorry to say this, but "new silicone won't stick to old silicone" is one of the old wive's tales that this hobby loves to spin out of control. New silicone applied to really old, dirty and in bad shape silicone is a bad idea. New silicone applied to clean old silicone that is otherwise intact is almost always just fine. It's not going to be a full strength bond, but in the case of replacing a single panel, where the only contact from new to old is the corner beads meeting each other, I wouldn't hesitate. Again, assuming the old silicone is clean and intact and not dirty or peeling.

While I'm on the soapbox, "RTV" is just a product name for one of momentive's silicone product lines. It's still silicone, it just has a brand name that borrows on the fact that it is room temperature vulcanizing (but, every silicone used in this hobby is, so it's not exactly a meaningful brand name). It is definitely good stuff and probably the easiest good silicone for a hobbyist to get ahold of, but it's still "just" silicone, in the end.

It's hard for me to personally make a judgement call on this tank. So much depends on a person's own approach, skills, and risk tolerance, not to mention details that aren't apparent in the photos. Even a brand new DIY'er can repair something like this, if they're careful and take the time to learn, but as everyone has said, it's not something you want to mess up. What's the thickness on the glass? I don't think I saw that mentioned. I am nervous about the tank after seeing how the bottom eurobrace was applied. The whole "squirt a wiggly line of silicone and drop the glass onto it" approach just strikes me as sloppy, even if it is technically good enough to hold.

[ca1ore]

Originally Posted by ozorowsky

Thanks all! Online I see this bottom glass replacement for 346 shipped from admglass.com. That is also tempered glass. I guess I didn't know this was a custom built aquarium. I'm attaching pics of tank/damage. From what I'm reading here, there's hope as the bottom glass is truly on bottom. It doesn't sit inside the edges. I'm going to call glass places tomorrow see how much they would repair (properly) for. Just sucks cuz this is such an awesome tank.

Initially thought it might be a glass cages tank, but it's not. May have been made by a hobbyist. Would make me nervous.