Angelfish
Pygmy angelfish aggression and compatibility
Article By Scott W. Michael
When it comes to aggression and compatibility with other fish, there is interspecific variation in the genus Centropyge. Some species are typically very aggressive, whereas others are not. For example, all the members of the "argi complex" (C. argi, C. acanthops, C. aurantonota, C. resplendens) tend to be very belligerent not only to related species but any fish, especially those introduced to the aquarium after them.
Because the members of this group are small, they are often housed in small aquariums, which is the worst thing you could possibly do if you plan on keeping passive fish (e.g., seahorses, pipefishes, batfishes, leopard wrasses, flasher wrasses, highfin shrimp gobies, fire gobies, dart gobies) in the same tank.
Angelfish in the argi complex are best kept in larger tanks with a lot of hiding places and no passive species. If you do keep them with less aggressive species, introduce them after these fish have been added and acclimated to the aquarium. Some other species that have a propensity to be aggressive are the flame, lemonpeel, halfblack, Potter's and multicolor angelfish (Centropyge multicolor).
If you want to keep more than one pygmy angelfish in the same aquarium, you will have greater success if your aquarium is 70 gallons or more and is packed with hiding places. When arranging decor, a series of coral heads is better for dispersing individuals throughout the tank than a long contiguous reef. Add all the individuals you intend to keep together (of course, after they have been quarantined) or add the smallest individuals first, followed by a larger specimen.
The goal is to have only one male per aquarium. In those species that display permanent sexual dichromatism, this should not be difficult, but in those species in which the sexes are indistinguishable, it can be a guessing game. Males are usually larger than females - at least the females in their harem. So, the greater the size discrepancy between two individuals, the more likely you are in acquiring a male and one or more females.
Also remember that in the absence of a male, females may change sex. Therefore, females held in a retail, quarantine or display tank too long before being exposed to a male may change sex. Although it was once thought that sex reversal was not possible, recent observations suggest that in some angelfish a transforming male may be able to revert back to the feminine sex. But a dominant male may kill a subordinate male or transforming female before they can complete this process.
Another way to possibly curb the aggressive tendencies of your pygmy angelfish is to house them with larger fish. They are less likely to engage in frequent bouts of aggression if potential predators are present. I'm not recommending keeping them with fish that could actually eat them. Instead, include some fish tankmates that are three to five times larger than they are (large angels, some butterflyfishes, large wrasses, large anemonefishes, surgeonfishes), and your Centropyge will be less likely to attack similar-size fish with reckless abandon. At the same time, keep in mind that some of the more timid pygmy angelfish may be affected negatively if intimidated by larger tankmates. They may refuse to feed and may hide all the time.
Angelfish Care:
If you want to keep more than one pygmy angelfish in the same aquarium, you will have greater success if your aquarium is 70 gallons or more and is packed with hiding places.
they should not be exposed to the physical stresses of a newly established marine tank. The aquarium should be set up and running for three or four months before adding any species of angelfish. This ensures that the nitrogen cycle in the tank has been completed and the levels of ammonia and nitrite are so low as to be immeasurable.
Acclimating Angelfish is very important, as these fish have been known to go into shock.
Before purchasing a pygmy angelfish, examine the sides of the fish very carefully for raised scales or red areas.
Angelfish Related Articles:
Pygmy angels captive breeding. If you want to try and breed pygmy angels, the aquarium should be at least 75 gallons and should contain a lot of rockwork and/or artificial coral to provide ample shelter sites.
Pygmy angelfish in reef tanks. Are these fish a threat to your invertebrates?
Looking at their natural diets, it would seem as though they would pose no threat to sessile invertebrates. However, most of these angelfish do feed on detritus, and coral slime falls into this category. So, although they usually do not feed directly on coral polyps, they will graze on the slime they exude.