How much weight can a glass tank take?

I like real rocks in my tanks. I started to add a vertical monolith and stopped, because I don't want to over stress my tank. I have heavy rocks in my other tank, but I'm concerned because the weight on this one is vertical instead of spread out horizontally.

I have several inches of substrate, so it isn't like the rock in directly on top of the glass, but I'm still looking for reassurance.

I'm sure you don't want to rescape your tank, but many folks who have reef or other heavily-hardscaped tanks will place 'eggcrate' lighting diffuser at the bottom of the tank to help redistribute the weight. Your substrate will probably serve the same function. Just be careful!

Edited by Newt, 11 August 2008 - 04:54 PM.

Thanks, I'd never heard of that type of egg crate before, good to know for future reference though you're right, I think I'd chose a smaller rock before I torn into the substrate.

Be careful with stacking or resting rocks vertically on top of a substrate. All it takes is a little bit of digging in the right place and the rocks can become very unstable. A rock slide can do a lot of damage inside a glass tank. I've seen it happen with burrowing gobies and shrimp. I'd imagine a crayfish or some sort of nesting behavior could do it in a native tank if your substrate was light enough.

If you're looking at stacking rocks you might look into some marine aquarium epoxy. It is commonly used in reef tanks to basically glue rocks together. If you're just standing up a single large rock you might try something like epoxying it to a ceramic floor tile or a big flat piece of slate to give it a more stable base and then burying it under the substrate. It'll distribute the weight more and it'll keep it from falling over.