Polyurethane Foam

[Denis]

Bill told me that it's just of the shelf PU foam you buy at Home Cheapo. The kind used for insulating windows and cracks.
You can now buy non expanding kind and also Crappy Tire has a grey version as well, according to Bill.

[Bartman]

Is PU foam safe in a reef tank? Anyone got pics of what it looks like?

[Bartman]

Nevermind. It's in the reference library.

[dreef]

"Great stuff" by dow is what you want to use.You can find it practically anywhere as it's a top seller.

[GMGQ]

Yeah like a lot of stuff we put in our reefs, it's SAFE after it's completely dried/cured.