The Flagfin Angelfish Apolemichthys trimaculatus is a very pretty, moderately sized angel. Bright yellow overall, it is accented with an alluring purple mouth and a prominent black spot on its forehead and can reach up to 9.8" (25 cm). It is also commonly called the Three-spot Angelfish because of the spot on the forehead, one above the eye, and a faded spot behind each gill cover.
The Apolemichthys genus contains only 9 species of angelfish with the Flagfin being one of the most commonly imported. This group contains some of the hardiest of the angelfishes, but unfortunately the handsome Threespot Angelfish is not one of them. are not easy angelfish to maintain in the aquarium long term due to their dietary requirements.
These angelfish are difficult to keep and so are suggested for more experienced aquarists. They are extremely timid and easily stressed. Consequently they don't handle shipping very well and are easily intimidated, then they only want to eat foods they recognize. Their natural diet consists of sponges, tunicates, benthic algae and weeds. Adults and very small juveniles are especially difficult to ship and generally refuse to eat. Its best to obtain young specimens between 2- 4 inches (5 - 10 cm) in length as they the easiest to acclimate.
The ideal tank for them is a mature reef type aquarium that is at least 100 gallons (378 liters). They need rockwork creating lots of caves for refuge, a lot of open swimming area, and tank mates that are peaceful. They do tend to be picky feeders, especially as adults. So having live rock and a good algae growth in an established tank can help them to acclimate. You can also help them acclimate initially by providing sponges until they learn to eat the new foods that you are providing. Once established however, they will accept a variety of aquarium foods. Be sure their diet includes plenty of plant matter. Offer prepared foods that contain spirulina as well as sponge material and meaty foods.
This angelfish can be kept in a community aquarium and even mixed with other angelfish if the aquarium is large enough. It is a semi-aggressive but can be easily intimidated when first introduced to the tank. The best tank mates are those that are not overly excitable feeders or overly aggressive. This angelfish is considered one of the safer choices for a reef aquarium as they tend not to pick on sessile invertebrates. But as with many of the large angelfish, an older adult can start to reek havoc on the reef, so be cautious. In a reef setting they will eventually eat most of the sponge and any other corals, so are not a great candidate for a mini reef.