Haven't bought any yet. I was curious, b/c the employee at this store mentioned they pair up in their tanks for spawning. Wanted to see other's exp. Not even fully sure if I would want to add this to the 50. Their unusualness has me intrigued, but don't wanna overload the 50. Was thinking more a down the line thing, maybe something in small pops to keep the ole' 10 running. For that, I was thinking 5-6 of them... but would limit their ability to run.