Placing Thermocol sheet below NON liverock

My friend gave a very heavy piece if ocean rock that is not a calcium carbonate LR but a hard proper rock that is hollow and beautiful. can i place a thermocol sheet below it? is thermocol bad for Marine tank? iv been keeping them in my FW tanks. the glass is just 6mm thick, so a bit scared of cracking it. here is the pic of the rock.

 

anyone?

 

looks like a meteor! cant help ya though! so BUMP

 

Idk what thermocol is, or that rock, but neither sound like anything i want in my tank. But ill bump it for you so ppl can chime in.

 

Don't know what thermocol is either, sorry.

 

Thermocol is styrofoam..... in my country its called thermocol

 

You learn something new everyday. Now with that tid bit of info. idk what the molecular structure of it would do exposed to salt water over time, i know i used it to hold my mangroves vertical. but underwater... idk man... why not just a DSB?

 

well the prob is tme sand will be 1.5" thick. not going for dsb, and even if i did, there are lots of fishes who love digging and dont want the rock to tumble. i had a cichlid tank and this did happen, entire 6yr old tank glass broke but fortunately no fishes died as they are hardy and i was there when it happened. can u use undergarvel filter plates, i have many.

 

Try Starboard or just some PVC...

 

small pvc stand? will that be good? any one tried undergravel filter plates?