Star Fish

Most make a nice addition as a clean up crew member; however, I believe the Green Sea Star or Brittle Star will eat fish. But I have several with no problems.

 

I have had 2 in my tank for nearly 2 years with no issues. That being said they aren't that big and have heard of people having problems with large green ones. Mine are tan and black

 

The ones that I have had were impossible to kill. they would loose whole limbs and would still grow them back with no problem. The only way one died was in a sump and the heater failed in the off position. As for being peaceful it would eat dead or dying fish but it could not catch an active healthy one.

 

Brittle stars are good sand sifters, I've had tons in my tank since day one and never had any of them eat any fish, let alone bug anyone! I've heard sea stars are pretty cool.

 

I've got a brown one that's almost 10 years old now. Got it as a hitchhiker, now it's huge. Doesn't bother anything. +1 on the green serpent being the fish predator from all I've read.