Safe to mix in tank?

[kwirky]

I had a plug of favia with a little piece of capnella or the likes on the same plug. The capnella was very small, but it started to outgrow the favia, until the favia grew a polyp right next to the capnella. The capnella died almost overnight. Bit of a shame, since the capnella piece was about 1.5" long. It was only about 1/8" when I first got the plug.