Too Much Weight Causing Leaks?

I've had a 40 gallon tank a few months and never had an issue. Last week I drained it, added rocks/substrate, and filled it up again. About a day later there were wet spots on the black frame on the bottom-front side.

Assuming this was a sign of a leak I removed everything and did a leak test. Five days later there were no issues.

When I set things up for a second time I noticed the same 'leak' along with a slight water decrease overnight.

Is it possible that the weight of the rocks and substrate is causing the bottom frame to leak? How much weight can a fish tank hold? And, is there Way to stop this kind of 'leak' without taking everything apart again?

 

I would look at the surface that you have the tank sitting on first to make sure it's perfectly flat. If not the combined weight of tanks with substrate, rock, and water could cause flexing which could ultimately lead to seam failure. The tank needs to be supported on all four corner.

 

quite unlikely.

Doesn't drip any water from the lid ?

 

Rember, a gallon of water weighs in the neighborhood of 8 lbs.
When you add substrate, rocks and other decor, it displaces water. How much displacement depends on the density of the introduced object. An eight pound rock is probably not going to displace eight pounds of water, but it might displace five pounds of water, causing a net gain of only three pounds. There are mathmatical formulas that can provide better estimates. I'm not quite nerdy enough to know the formulas. Glass can hold an unbelievable amount of weight if positioned properly, where the weight is distributed evenly. I've had over 200 lbs. Of rocks in a tank at one point. Regarding your leak. You might have condensation forming on the upper lip of the top brace, which seeps out at a corner joint. Lowering the water level a bit usually solves that problem. If that's not the problem, toss the tank. 40 B's are very inexpensive.

 

I doubt the stand is the issue. I custom built it and the tank sits perfectly with all 4 corners touching. The entire exterior of the tank is dry, except the area immediately above the black plastic piece on the bottom.

 

Unless you are putting some hellacious rock in there, (which btw would break the lower glass) the addition of rock and substrate is not going to cause a leak on your tank. The pressure on the bottom edge of the tank due to atmospheric pressure applied to the surface and the height of the tank will outweigh in this case the substrate. I can discuss compressive stress and elastic stress if you want but you are most likely not seeing a leak.

 

Rocks can't overload but they can unbalance. Remember water pressure is 100% equally distributed, meaning if you add a cup of water, the weight of it hits all edges/corners equally. But a rock isn't liquid, a cupcshaped rock ina corner affects only the silicone in that corner... The weight is focused.

 

Well now that I've removed about 5 gallons everything appears to be dry. I'm going to add that back and see what happens

 

Turns out the issue was a crash in my pump caused water to leak down the back side of the tank. Repaired it with silicone and everything works!