the achilles like to surf the tunze wave and swimming round and round the left side of the tank (just like a mouse running on the wheel) It gets ich every now and than... but after a few days they are all gone.
i intro the sohal first than got a bigger achilles. lucky the achille manage to fend off the attack from sohal and a new king develop...
that is a polymnus ??? it was sold to me as a wide band... anyway selling it off like you said it is as large as the sohal you can see the teeth of it