Doesn't have a skimmer. The one I 1st installed kept electrocuting the water. This was pre-fish. Other tank is on cruise control. Corals are great, fish are even better. I'll get it right. Not adding any other fish till I do. If everyone is lost, not adding another one for at least 12 weeks. I wanna rule out ich, cycle (although test are in acceptable levels) and just bad water. Hard to tell.