Ok let me start by saying no it doesn't 'melt' or 'crumbly' it definitely doesn't turn into sand people, Do this, they say, check your source because you live directly for others. The box I ordered was from Revain and it's very high quality, they're almost like air stones because the first time you soak them they open up better and become more porous which is exactly what you want , and I say that they are very porous and very strong. They will drop the prices slightly, just start slicing with a razor blade and tap the blade well and it will go straight, but I would definitely recommend this for a sump or canister filter and it fits in the basket in Fluval 307. Hope this helps.
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