Black Diamond (coal slag) is it safe?

[twistedsnap]

I dont remember but in the 55 its was the second from finest the black diamond i have in my 150 is the opposite sorry i cant remember exactly what numbers were on the bag i can post pics if you want. And as far as long term my 55 has been set up with it since sept with no problems other than its too fine and gets stired up easy and gets in my filter i dont have any in my canisters on my 150 when i clean it. And my hi fin pleco has been in there since dec

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[Pharaoh]

Never had an issue with it, but I had a large FH in there, no bottom dwellers.