How much weight

[KaiserFish]

How much weight can a tank support?

I'm looking at adding more rocks to my cichlid tank, but am concerned as to how much weight the glass can actually support.

Theres alot of nice rocks in our new houses backyard that are about the size of a childs head, and would make a great base for caves in a 90 gallon tank mixed with various pieces of slate, etc.

I have a sand substrate ~3-4 inches deep (or more or less, depending where they've dug sand pits and made sandhills)

 

[JohnPaul]

Remember, water weighs 8.3 pounds per gallon. So if you are talking about your 90 gal tank, that's about 750 pounds that the glass is supporting.

Compared to that, a few 5 or 10 pound rocks isn't going to make the slightest difference.

 

[KaiserFish]

Thats kinda what I figured. Since the basic design of a tank also distributes the weight across a larger surface.

 

[QTOFFER]

You should be able to put in as much rock as you want, but you want to make sure they aren't creating any pressure points against the bottom glass. The best way to do this is to place a piece of foam, flat slate, or eggcrate) under the heavy rocks to distribute their weight better.

 

[shawmutt]

Using eggcrate, I had about 50# of rock in my 30 gal tank with no problems.

 

[severum mama]

I have about 70 pounds of rock in my 55 gallon. I put it in there before I had heard of using eggcrate 8O but so far it is ok...
You shouldn't have any problems.