Fixing a leak


New member
my 12" cube tank has 1 flaw. When they built it they did not continue the silicone all the way to the top of the tank. In one corner it stops about a quarter of an inch before it reaches the frame. Every time I slightly overfill the tank or reach my arm in the tank it causes it to drip from that corner.

I want to now if it is possible to silicone the leak wile the tank is full. Can I drop the water an inch or 2 and fix it?

Will chemicals in uncured silicone pose any kind of threat to my corals or fish?

How long would it take to dry?

What brand to you recommend?



New member
since it's at the top and not under much water pressure, i would think this would be fine. I'd just use "aquarium silicone" from lowes.

You'll need to let it cure a full 48 hours before it's safe to expose to the tank water, IMO. Acidic Acid is what is curing out. It's not super dangerous or anything, but in a tank that small, it could definately do some damage.

Generally speaking, new silicone doesn't adhere well to old silicone and when fixing a tank, all the old silicone should be removed. But in this case, since the "patch" is not under water normally, and when it is, it's not under much pressure - i think you'd be fine.


New member
sounds good to me. its not a structural fix, since you arent going to get it into the seam, but no worries, just want to stop it from leaking, and that it will.

Gold Stripe

New member
Make sure you get the glass super clean or the silicone wont stick well. Just wiping with water wont do it. You need to lower the water enough that you can wipe it with alcohol or some other cleaner without risk of getting it in the water by accident.


New member
I'd keep a close eye on that corner, even after fixing it. It'd suck to have the joint slowly separate over time.