strange thing in my tank?????

[ScubaSteve]

Ya, the mini brittles will get a little bit bigger. I have some that are about 1" to 1.5" in diameter. They're harmless. At last count I had over 20 in my tank. They mostly just sit in the rocks with their arms sticking out or they hang out under the sand. They're harmless and are kind of funny to watch. Don't worry about them.

If your brittle star grows to epic proportions it's probably just one of the big brittles that people love in their tanks. It might eat a fish, but it's doubtful. And I'll wager a pitcher of beer that it won't even grow that big.