floor support for heavy tanks...?

[SAT]

That seems like a good idea. I suggest a piece of 3/4" plywood.

 

[suprzman]

You think the weight would be properly distributed over the length of the plywood? Or would it be more likely to push down in the center of the plywood itself, possible causing that to sag?
Thanks,
Z.

 

[SAT]

3/4" plywood is pretty rigid, much more so than most floor materials. Use exterior grade so it won't come apart if it gets wet.

 

[Hardip]

For my 400/500g tank, I am looking at creating shuttering support under the joists and filling it with concrete. This is the only sure way.

With my current 180g tank, I am a bit suspicious of the floor even though I have the tank against one of the walls that supports the joists.