So I was having trouble sleeping last night and I was up at about 3:00 AM cleaning up my prop tank and area. I was wiping some salt off the glass of my sump/fuge tank, when I discovered a (GASP) crack in the glass!!! The salt I was wiping up was actually creeping from the crack, and after all the work I have put into this so far, I nearly fell on my butt.

I don’t know how long the crack has been there. Don’t know how it happened. I *do* get a stomach ache when I think about it.

Now it’s the following day. While I am not very happy about this, I also don’t necessarily see it as being the end of the world.

Right now, I have three options. I would love input to help me make my decision.

Option #1... I have a two part epoxy product called PC-7. You could probably glue two CARS together with this stuff. It’s probably the most amazing adhesive I have ever used. It cures in 24 hours, and I would guarantee that if I took that tank to my roof and threw it on the patio, the part glued would still stay intact while everything around it shattered. That’s the good news. The bad news is it will be ugly, but it’s hidden behind my skimmer anyhow. It will be a big dark grey blob/line across the tank. I think I could live with that. I’m fairly certain it would restore the structural integrity and seal any leak.

Option #2... through this process I have been totally amazed at how strong silicone actually is. My thought here would be to get a piece of acrylic or glass, and spread a thin layer of silicone over the whole thing, and then just stick it on the tank over the affected area. I know silicone will seal the leak and the strength would probably be good as well.


Option #3... I replace the tank, which will be a complete pain in the toockus. I could do that, I have a spare 29 gal sitting around, but I would have to make new baffles, moving the refugium would be a total pain... option three is without any doubt a “last case” scenario.

So let me know what you think, I feel like I should take immediate action (e.g. Today) to fix this problem.

I don't believe there should be any scenario besides option three. You cannot repair cracked glass. Sorry... not what you were wanting to hear, I know.

for the most part, i agree with Renee
there are two things i want to add

1.) if its at the top there really isnt as much stress on it as if it was at the bottom
2.) it being a small tank over all that too lowers the stress..

if this tank was any larger or if the crack was anywhere else but the top i would not chance it..

however in this case, you *may* be able to get away with it

all this said, Renee is still right, you can not restore the structural integrity of glass, and what you maybe doing with the glue is moving or creating new stress points.
im not a structural engineer and wont pretend to know the details

in short my official recommendation is to use option 1 and/or 2 only until you can proceed with option 3

my un-official answer, you might be able to get away with just option 1 and/or 2, but if it were me personally, i would set aside a weekend and replace the tank, especially since its small

What is this tank set up again? How big?

its a 29 gallon frag tank, IIRC

i agree with our fearless leader. only use option 1 and 2 until 3 can be employed.

if you need another 29 .... i have one you can have, just pay shipping.

You cannot repair cracked glass. Sorry... not what you were wanting to hear, I know.


glass in general can be repaired, i.e. my windshield has been repaired. I've had it sealed twice so far and it hasn't spread- it's been over 5 years since the rock hit it.

I know a windshield doesn't have the same amount of pressure on it, but maybe it's possible? At least the tank would have a constant temperature.

It would be the risky option.

Ummm... I don't know about that..... A windsheild is safety glass not the float glass on our tanks.... a whole different monster.

I have honestly never heard of someone fixing a glass tank besides replacing and resealing the panel. But I'm all for someone else being a pioneer and going against the odds. I just wouldn't be the one to recommend it and feel responsible for it.

Is the 29 gallon a sump for a larger tank?

I might be a little late on this but i would replace the tank and here is why,

1. All the work that we put into our tanks. We spend alot of money and work trying to get our tanks to look great. (salt water great) and after all the money we spend i feel the tanks are the cheapest to replace or buy.

2. If the crack is near the bottom and it decides to get worse either now or after its repaired then the water will drain so low that it could kill off stuff and create a big mess and the leak could also be a fire hazard. (depending on location of the crack to outlets and other cables)

3. The effort you put into fixing the crack would probably come close to equally around half of the time it would take to replace it. I replaced a tank for a friend of mine in about 3 hours. It was a 40 gallon tank that had a large crack in the front.

I just think it would be a good idea to replace instead of repair. For a hobbie that we care so much about what would be 3-4 hours of work to assure a fix. IMO and IME

glass in general can be repaired, i.e. my windshield has been repaired. I've had it sealed twice so far and it hasn't spread- it's been over 5 years since the rock hit it.
yes, windshields are quite different.
they consist of multiple panes of tempered glass with a layer of a plastic like material between the panes. all of these layers are sealed together.

when you get a rock or stone chip it usually doesn't go through, it hits that hard plastic layer and stops. sometimes it does go though.
the spider cracks that occur, usually only occur on the upper pane of glass.

when they "fix" such holes, what they do is drill it open then pump it full of glue. this action is simply to hold it all together so no more spider cracks occur

obviously this is not even possible since we have a crack, not a chip that lead to a crack, and the glass is not multi paned