Cleaner Wrasse
The iconic black-and-electric-blue bluestreak that sets up cleaning stations and picks parasites off other fish — mesmerising on a wild reef, but one of the hardest common marine fish to keep alive. It is an obligate cleaner that often will not switch to aquarium food and slowly starves, so most experienced keepers discourage buying it. It harms neither corals nor inverts, so it stays reef-safe; the problem is survival, which makes it an advanced (and ethically fraught) purchase.
Tankmates
How Cleaner Wrasse gets on with the rest of the reef, checked pair by pair by the same engine as the live pre-flight.
Best kept apart
A real clash — aggression, predation or a same-genus fight.
Keep an eye on these
Usually fine, but worth watching in a smaller tank.
Good tankmates
No conflicts — a few popular ones to start with.
