I've read that untreated polyurethane foam rubber is fine to use. The kind of stuff used in furniture, I actually read that in a pacman book. I can't seem to find a good source of it anyway.. I'd just use the filter or like I stated earlier that Matala filter, I don't think they can burrow and tear into that. They tear lots of holes in the blue stuff and my frogs have practically tore up a whole $15 roll in a month. I'm going with matala next time even though its more expensive, I think it will last a lot longer.

As far as hiding goes, you can always put some sphagnum moss in a corner or some fake plants as hides, that what I use. As long as your temps are at a fair level the frog shouldn't get too stressed from not being able to burrow, as long as he can hide somewhere. I don't think I'd put a frog thats spent its whole life in eco earth on foam though, that's just me. I imagine that might be somewhat stressful. Babies that will grow up on foam, that's another story.

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There you can see what I mean about the hide. She eats like a champ and doesn't show any signs of stress at all. She actually grew up on that foam her whole life WITHOUT a hide in the middle of a kitchen. She now has a hide and uses it constantly.