The Emperor Angelfish

There are many beautiful fish available to the marine aquarist and one of these is the Emperor Angelfish, properly called Pomacanthus imperator. Purchasing this fish when young gives the aquarist in effect two fish over time.

Some fish can be recommended without qualification as they are not problematic. This is not so with the emperor unfortunately. There are clear constraints and also the fish could find the surroundings too much to its liking!

First it is always assumed that seawater quality is excellent, as it should be of course – this is a requirement for all marine inmates. The next problem is size, or eventual size anyway. Many emperors are sold as juveniles at say 3″ (circa 8cm) or so. They are so beautiful that the aquarist could be tempted and lose that oh so important discipline. The fish is transported home and settles well. Unfortunately, this little fish can grow to around 1ft (circa 30cm). This is clearly going to be a problem for many aquarists as their aquarium just isn’t big enough. The minimum sized aquarium should be 100 gallons, better around 150 gallons or more, the amounts exclusive of any sump. If the aquarist has an aquarium of sufficient size, fine.

The fish is not for a reef aquarium. That short statement knocks the suitability of the emperor on the head for many aquarists even if their aquarium is large enough. Again, large aquarium or not, resist the temptation because the emperor could find your reef very likeable, including the corals, tube worms, shrimps when moulting etc. They are likely to be nibbled at or eaten, not something that is going to endear the fish to the aquarist. So there’s the next constraint, the emperor needs a fish only system. It should also be remembered that the emperor will not be happy with another emperor, or any fish with colouration similar to its own. So the large aquarium could have an emperor plus a few others, remembering that fish size reduces the number of fish the aquarium can house.

If the emperor is still considered a potential addition to the aquarium, then feeding is the next consideration. Emperors are not particularly picky but do require a suitable diet to maintain colour and health. There isn’t any reason why decorative ‘live’ or ordinary marine suitable rock should not be in the aquarium, remembering that swimming space for the fish is required. If this rock has algae growing on it then the emperor will graze it regularly. It’s unlikely that the algae will survive and reproduce quickly enough, so various chunks of rock can be selected and, one by one or more as necessary, taken to another tank or lit sump and left to allow algae to develop. This way there will nearly always be a rock for the emperor to graze on. This green diet can be supplemented by the use of blanched lettuce leaves and algae that can be purchased from a shop. ‘Vegetarian’ flakes could also be of some use. The green content of the diet should amount to at least one third, the rest can be made up of frozen food such as shellfish, krill etc. Marine flake food can also be fed. Failure to feed a suitable diet could well result in a ‘sad’ fish – malnourished, poorly coloured and ill. Juvenile fish are likely to begin to fade more quickly.

Juvenile Emperor Angelfish

Ok, so the aquarium is large enough, the aquarist is happy with the restrictions of size and potential tankmates, and diet will be properly followed. The beautiful emperor will be a wonderful addition, it shouts of the colour and vibrancy of the reef.

The extra that the aquarist achieves is, as mentioned in the first paragraph, the equivalent of two fish. When obtained as a juvenile the colours and patterns are completely different to the adult and the gradual change can be observed. Both versions of the same fish are beautiful, though the adult emperor is more imperial. I don’t know if the correct reason for the two different fish patterns is known, but it has been thought that the juvenile is protected from any unwanted attention from adults.

It must be remembered that the emperor is not suitable for every aquarium, space is needed and if a coral reef is desired the fish is not suitable. There are other fish of this family that are similar in this respect. Discipline, patience and research are the watchwords – there are other fish that can enhance and not damage a reef and plenty suitable for those with a smaller aquarium. But if everything is suitable for the emperor – including the aquarist! – then wow, all acknowledge the emperor of the reef.

(Photo: Emperor Angelfish –

(Photo: Juvenile Emperor Angelfish –

  1. Thanks writing about The Emperor Angelfish
    Loved it!

  2. Glad to see a comment like yours.

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