They congregate in large groups and many times live in small, close quarters to each other. Now, you take a few Yellow Tangs, place them in a tank together at one time and generally they will reside peacefully with one another. However, now try and put a new Yellow Tang addition into the same community where the others have already been living. What happens? Usually instant harassment begins, many times results in the eventual death of the new addition. Why? It's called being territorial. The Yellow Tangs have established their little family, and even though the new Yellow Tang is one of them, for whatever reason they still see it as an outside intruder.
In most cases fish will particularly attack fish of their own kind, and many times those that are similar in shape, color or size, if they are introduced later on into a community. This territorial behavior is common in almost all fish, as well as other marine animals. It can be a response to something as simple as one fish straying into another's so-called "territory", one fish protecting its mate, or a mated pair of fish protecting their spawn or nesting area. That is why most fish books suggest only putting ONE fish of any ONE particular species in an aquarium, unless they are introduced all at the same time, they are provided a large tank with ample housing, you have a mated pair, or have a species that will accept this type of relationship. For example; Lemonpeel Angefish can be kept in trio's (one male-two females), if in a larger tank with plenty of hiding places.
If you want to add another fish into an already established fish community, assuming you have chosen an appropriate species, here are some of the ways that you can introduce them to help reduce problems of harassment.
- Remove all the established fish from your aquarium. Rearrange the decorations/rocks and then place ALL the fish back into the tank, including any new ones, all at the same time.
- Place a well ventilated plastic barrier in the tank to keep the new introduction separate from the other fish for a few weeks until they get used to seeing each other. Martin Moe, Jr. suggests this method in his Marine Aquarium Handbook.
- Place the new introduction into a cage or well ventilated box and keep separated from the other fish for a few weeks until they get used to seeing each other. When we visited the Pacific Beach Hotel to see their 280,000 gallon Indoor Oceanarium, we found out from Jane See, the curator, that this is the method they use.
- If all else fails, ask your local fish store if they will take the fish back in exchange for another fish is more likely to be more compatible with your tank community. Most good suppliers are more than happy to help you out.
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