Unwanted life in a tank

[fastzorro]

What (is any) would be any unwanted life to look for?

 

[Bifferwine]

The two most common anemone pests that are unwanted are aiptasia and majano.

Colonial hydroids are another pest.

Mantis shrimp are cool critters, but can wreak havoc on your other animals. And gorilla/xanthid crabs are also considered pests.

 

[Smitty]

+1 Biff

 

[DAvis]

This is an algae you don't want! Red turf algae. It is very difficult to control when it gets established. You can see my goby is NOT amused!