The powder blue tang (Acanthurus leucosternon) is a breathtakingly beautiful, widely recognized (even among non-hobbyists) marine fish that can be a real pain to maintain in aquaria. While it is possible to keep one successfully under ideal conditions, most specimens that enter the aquarium trade unfortunately perish within a short period after purchase.
Why such a dismal survival rate? Actually, this species has several points working against it as an aquarium candidate:
- It’s highly susceptible to ectoparasites, such as marine ich (Cryptocaryon irritans).
- It has to travel a really long distance from the point of collection in the Indian Ocean to the hobbyist’s tank (depending on where in the world he or she lives, of course), and it can get pretty beaten up and starved en route.
- In nature, individuals claim a very large territory (much bigger than your average home aquarium), which can translate into hyper-aggressiveness toward any real or perceived resource competitor in aquaria.
- It is more demanding with respect to water quality than many fish commonly available in the hobby.
- Captive specimens don’t always learn to accept standard aquarium foods.
Despite these drawbacks, success with A. leucosternon is possible (though never guaranteed) under ideal circumstances as I’ve mentioned. So, how can you improve your odds of keeping a powder blue tang alive and thriving? Be sure to:
1) Provide a large, mature aquarium
I would consider a standard 125-gallon aquarium to be reasonable minimum housing for this species, but the bigger, the better. You want to ensure this fish has plenty of horizontal cruising space as well as ample live rock to nibble upon.
It’s also important to let the system mature for at least six months prior to introducing the specimen so parameters are stable and a steady crop of algae is available for grazing. A “sterile,” newly set-up system is not a good environment for A. leucosternon.
2) Choose a healthy specimen
Make sure any specimen you’re considering is robust-bodied, not thin and emaciated; appropriately active; uninjured and showing no obvious signs of disease; and demonstrably eating. If you have any doubts, pass the specimen by. Remember, the odds are stacked against success with this species, so any questionable behavior or symptoms in a prospective specimen should give you pause.
3) Quarantine the specimen for at least a month
This is always good advice, but given the powder blue tang’s disease susceptibility, skipping this step can be particularly reckless. Also, make sure the quarantine system is sufficiently large (I would recommend something at least in the vicinity of a 29-gallon tank for quarantining this species), has a mature biofilter, and offers the same exceptional degree of water quality it will (or should) enjoy in your display tank. Be prepared to do frequent water changes! I would also advise performing a freshwater dip as a hedge against ectoparasites before introducing the specimen to quarantine.
4) Maximize water movement
A. leucosternon demands robust circulation and a high level of dissolved oxygen, so be sure to provide ample turbulent water movement, not only throughout the water column, but also at the water surface to maximize gas exchange.
5) Minimize dissolved pollutants
Think: oversized protein skimmer and copious water changes. Also, the system should be minimally stocked and judiciously fed to keep the bioload to a minimum.
6) Avoid similar tankmates
7) Go heavy on the greens
In addition to a good crop of algae growing in the aquarium, A. leucosternon should be offered a varied herbivorous menu, including items such as dried marine algae sheets, frozen herbivore formulations, algae-based flakes and pellets, and so forth. Several daily feedings are recommended.