not sure to be honest, but see posts on raw shrimp cycling method. I used it for both my tanks. Basically put a couple shrimps from the seafood section of your grocery store (raw) into some type of mesh bag. Put them in your tank. The bag makes it easy if you want to take the shrimp out. I actually didn't use a bag for mine, but left it in for the hermit crabs to finish off after the cycle was complete. The shrimp decomposes giving off constant fuel for bacteria growth.