I have a piece of 1/2 pink board under my 180 and under my 100 gal
prop tank. The insulation board sits a 3/4" plywood too though. Not sure it does anything but I heard it could help so I added it
Definitely does not hurt
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,