[Sikkob]

Go with live sand, since you are looking at a fish only tank I would get dead sps coral within a couple months it will actually be live rock and help support the bio in the tank as well as grow algea.

When you say organisms do you mean other fish and crabs? If that was your question then the answer is yes. I had a dwarf lion with a powder blue tang. A very important rule is never feed it fresh water food, feed it silver sides, shrimp and squid. There is a chart somewhere within the forums and many online to see compatibility...there are also different types of lions as well.