<a href=showthread.php?s=&postid=13446547#post13446547 target=_blank>Originally posted</a> by SlowCobra
The fact that you are even asking about putting it in a 50 or even a 100 gal tank shows you have a lot of research ahead of you.
Achilles need at MINIMUM a 180 gal tank to come even close to leading a HEALTHY THRIVING life. They do much better in 8ft+ tanks. They are considered an expert only fish for a reason. They have an abysmal survival rate in the home aquarium. It is rare to see someone have long term(RE: years) success with an Achilles. Those that have the best luck have usually done a lot of research and have designed their setup around the Achilles.
It starts out with them being extremely poor shippers. Many of them don't survive the shipping. I don't believe any of the online vendors will even offer a Alive Arrive guarantee due to this. They are an Acanthurus tang and like all of them are very susceptible to ich. They are generally not what most would consider a peaceful fish, especially with other Acanthurus in the tank. They like to let everyone else in the tank know they are the boss.
They come from areas with tons of crashing waves(RE: extremely high flow) with a lot of rocks. Essentially they need a glass cage setup that has the same conditions as it takes to have a healthy THRIVING SPS tank. Pristine water conditions, a lot of varied flow(at least 40x turnover in the tank), uninhibited swimming around the entire tank, a lot of rock work with a lot caves for them to dart in and out of.
To have the best chance of a long healthy life they need to be fed several times a day with a variety of different foods. They need to have plenty of Nori provided to supplement their lack of available algae. Treat at least one of their daily meals with Selcon and Garlic to help keep their immune system in check.
If any other questions feel free to ask, I have done a lot of research on the Achilles and tangs in general. In 3 days my Achilles will have been with me for 1 year. He is fat, happy, and eats out of my hand.