Putting incompatible fish together ranks with overstocking and overfeeding as one of the major causes of failure to keep marine fish successfully. Incompatibility takes three general forms:

1) One or more dominant fish bully an unrelated species. As the harassed fish becomes ore and more stressed, it is likely to succumb to disease which if infectious will spread to he rest of the livestock in the aquarium.

2) The territorial claims will creates disharmony among the livestock. If two members of the same species of an extremely territorial nature are introduced into the same aquarium, then the result will be disputes which can be extremely serious, leading to death of the defeated party.

3)  Many fish go “missing” because they are eaten by a tank mate. A predatory fish is often introduced as a harmless juvenile but given time will be eating fish almost half of its own size! Predators can only be trusted with species of the same size or larger.