This fish in addition to the regal tang is also known as the blue surgeonfish, but is properly called Paracanthurus hepatus.
The fish must be known to just about every marine aquarist. It is a beautiful blue with a yellow tail, with darker shading along the edge of the dorsal fin and along the back. It is often seen in retailer’s shops at a small size and the blue is wonderful – a small shoal of them is something else. I read somewhere once that the fish is the ‘bluest thing on earth’. How true this is could be questionable but it gives the correct impression. The wondrous blue does fade however as the fish gets larger.
The link shows a photo:
Talking of size it is possible for the fish to grow to around 11¾ inches (circa 30cm) though it is not so likely to reach this size in a home aquarium.
Seawater quality needs to be high which is normal for all systems.
As with all surgeons it is necessary that the fish has plenty of space to swim, therefore it is not suited to a small aquarium. They could be purchased at a small size but as can be seen they grow. They are usually acceptable for a reef system but the reef must not be so large as to over-reduce the available swimming space.
The fish when swimming seems rather inefficient compared to most others, and sometimes seems to be trying not to float to the surface. This is normal and it can move if the necessity arises!
Unfortunately, the fish is reported as being very susceptible to ‘white spot’ and ‘velvet’. I don’t dispute this at all though when I kept one for a good many years I didn’t encounter any such problems. However, Peter had a problem with ‘white spot’ a good while ago and sadly lost some fish before he cured it. One of the survivors was the regal tang!
As said I used to have a regal tang. When I cleaned the aquarium viewing glass with an algae magnet the tang would slowly approach the moving magnet and follow it up and down. Slowly the colour of the fish changed the blue getting more and more pale until it suggested white. It would continue to follow the magnet up and down with fins erect in a very obvious threat posture. The fish was truly pale with rage! The plastic of the magnet was blue so it was presumably seen as an interloper. Among its tank mates, including other blue fish, the regal tang was peaceable though. Maybe it took exception to a square fish!
In the aquarium they are generally peaceful and good eaters. The will take flake and the usual frozen foods such as brine and mysis shrimp. It is essential though that a supply of algae is provided to keep them in good health and colour. If there is insufficient in the aquarium, which is likely, then the aquarist must provide a regular amount of Nori or similar which can be obtained from pet shops and also health food shops (humans eat it with toast apparently!). The fish will also eat blanched lettuce with gusto, though this is not as good as algae.
If the fish is selected carefully in the first place, the home aquarium is big enough and a suitable diet is provided, the regal tang is a good addition to the display.