Selecting Compatible Fish

Take time to research and select fish that will live harmoniously together.

Choosing compatible fish for your aquarium is actually quite simple. But it does take some research. When looking for compatible fish, there are two basic guidelines to keep in mind:

  1. Size: A fish will generally eat anything that fits in his mouth — even his own offspring. Though some fish do exhibit parental concern, many abandon parenthood as soon as they lay their eggs. Their young are then left to fend for themselves. In general, a fish that will grow large will most likely eat fish that stay smaller — even if the large fish is peaceful and non-aggressive. Simply put, if a fish can swallow something, he will most likely eat it.
  2. Temperament: Keeping aggressive fish with peaceful fish is never a good idea. If two fish are the same size, or even if the more aggressive fish is smaller, the aggressive one will attack the more docile one until it is compromised. An aggressive fish may pick at the less aggressive fish until the victim becomes unable to resist disease or dies.


Steps to adding new fish

This simple method of addition allows the larger, more peaceful fish to set up their territories first — and thus have an increased chance of survival:

  • The first fish in your tank should be the least aggressive.
  • Add fish in order of increasing aggressive behavior with each fish being smaller than the last.
  • The last fish added to the tank should be both the smallest and most aggressive.


Remember: always do your homework before adding new fish to your tank. Every possible combination of fish has been tried and the success or failure has been written about on the internet.