What in the world!?

[Dieboldly]

Can anyone tell me why I have this under my live rock? I saw something looked like a bug go across the rock one day too....

 

[Rob909]

I don’t know what those are called but they’re harmless little filter feeders. They’re good for the water. The little bug was likely a copepod or amphipod. Both also good for your tank. They are a natural part of the cleanup crew that thrive in established tanks. They usually come via hitchhiking on live rock or corals. They are a natural food source for fish and some fish like the mandarin goby will ONLY eat those. All signs your tank is maturing.

 

[kno4te]

First thing I thought was a nudibranch of some kind.

 

[tlindsey]

Like stated harmless . You don't want Mantis Shrimp or Fire Bristleworm's coming out of the live rock.

 

[Deadliestviper7]

Probably pineapple sponges, harmless