I bought one on the popular auction site once. If you're like me, you probably have green hair algae. Sea hare's are highly recommended to mow it down. My sea hare did great until my cleaner shrimp picked away and eventually killed it. The hare inked the heck out of my tank (non-poisonous) and my skimmer had a nice purple froth in it. Anyways, as Beth recommended, you should research what the root of the problem is. Assuming that Green Hair is your problem, do some research on Phosphates and consider your water source (tap water etc.) Good luck.