Black powder?

[Ruth]

If it is the same stuff I am thinking of it is a Marc Weiss product and IME they are all hockus pockus crap. I tried using it for a while on a former tank and I cannot say for sure it was the black powder but man did I get a cyano outbreak - that would not go away. I was using canister filters with sponge though which was also contributing to high nitrates but my best guess is the combination of a canister filter and black powder = instant cyano.