To Poly or not to Poly?

[George Lopez]

Hello everyone I'm seeing up a new 90 gallon Glass tank and was wondering about polystyrene. Some people say to put it but isn't that only for acrylic tanks? My tank is not flat under as an acrylic would be, so all of the load would be only on the rim of the tank and if I put poly I'm thinking that it will just crush it. There is a sheet of 3/4" plywood that it will be sitting on but i just wanted to see if anyone could give me a better insight before adding water and never lifting it again (hopefully)

 

[Sacohen]

I’m setting up a 90 too, but I don’t plan on putting anything under the tank.
I’ve read that glass tanks don’t need it.
The load is on the rim as you said.
Best advice is check with the tank manufacturer.

 

[Mandelstam]

If the tank didn't have any bottom rim I would say you'd have to have foam under it to protect the glass from pressure points from sand or other small stuff. If the bottom is floating there's no real need for that. Depending on how much rock you use etc the bottom can deflect some and may end up touching the plywood (depending on the rim and glass thickness etc) so making sure that the bottom panel and plywood is clean without any grains etc is probably a good idea.
The bottom panel has to take both the weight of the water plus everything else you put in there so the pressure is higher than on the sides.

 

[Daniel@R2R]

I'm thinking it wouldn't hurt, but it's probably not necessary.