i agree and would just like to add to this post. have you considered filtration, lighting, etc. is it a reef, live rock, or fish only tank? the reef will require expensive lighting and perfect water quality and movement to suceed. expensive. the live rock tank is a step down, and the fish only easier but its just fish. most likely if its petsmart your hood/light is usless for a reef. it's gonna be 300 minimum for the proper lights for a reef. and minimum another 350 for filtration.
my suggestion is a live rock tank. you can get away with the hood that is included but will have to change the bulbs. 18k power glow, and a 10k coral life will get you by. ( one of each or 2 of each depending on hood ) 40$ to 60$. a good submersable heater 25$. some type of mechanical filtration - an emporer 400 dble bio wheel or a canister filter 55$ to 90$. and heres where you have to spend. get a GOOD protien skimmer 125$ + and atleast one good powerhead 35$+
make sure you get a deep sand bed. 3 inches or more. and seed with a few pounds of live sand ontop. your looking at atleast 75 lb.s of sand or 75$ dont skimp on the sand its VERY important. biological filtration is MORE important than mechanical. it starts in the sand bed.
live rock - two ways to do it. buy some dry rock/base rock and seed it with a few pieces of good live rock. and wait. or buy lots of good live rock. it aint cheap. research it its your choice. even if you go with a fish only tank the only thing you can subtract off of the list is the light bulbs and the live rock. everything else is bare minimum mandatory.
LIVESTOCK
for your 55 gallon reef - cleaner crew (snails, crabs, starfish, etc) 75 lbs of live rock, 3-5 nice corals/anemones. a few small clowns(percula, sebae, ocellaris, etc) or 1 larger species (maroon, tomatoe, etc.) 1 gramma or psuedochromis. almost any blennie or goby. and as for a "show" fish a dwarf angel or a butterly. ( monitor all dwarf's with certain corals and butterflys with sponges) a flame angel or coral beauty are my preference among dwarf's. and there are many butterfly's to choose from. the beauty of these tanks are not the fish but the entire habitat. high maintainance, expensive, but well worth it IMO.
55 gallon LR tank - 50 lb.s of live rock. cleaner crew ( although not as large as required by a true reef) clowns as above or chromis. large shrimp/large crab (coral banded shrimp or arrow crab). although not recommended you could have a tang in this tank. 1 TANG and a small one. and heres why. unlike a reef tank, if needed you can move stuff around. so if he eventually gets too big you can easily and safely remove him. in a reef you cannot. under 3 inches and only yellow, purple, scopas, sailfin and the like. no BIG tangs, no hippos, achilles, unicorn's etc... no powders! grammas, and psuedos are good here too. as well as goby's and blennies. "show fish" should be 1 juvi tang and ONLY the ones i mentioned. or possibly a dwarf angel and butterfly. be very careful of overstocking! 10 to 15 inches of total fish body length is a good indicator for your tank. a good skimmer, a deep sand bed, an adequate cleaner crew, and your diligence will take care of the rest.
Fish only - the question here is carnivore or community? a dwarf lion or a small grouper for a carnivore. and the above mentioned fish for a community. you can also add wrasses to a community and triggers to a carnviore. this tank alllows a few more fish if your diligent on water changes. carnivores require meaty and sometimes live foods and can foul up a 55 gallon quickly. although i have seen a 55 gallon with 2 lions and it looks awesome. any community tank will require places for the fishes to hide. it can be LR, pvc, ornaments, etc. so even a fish only tank will require something. this is true for carnviore tanks too if you have triggers or groupers. you could max out at 20 inches of fish in this tank if you know what your doing
A) you should add fish to the aquarium based on their adult size.
B) can you physically fit a juvenile in there? yes. should you? no. these fish are cruisers. they dont sit on one rock in nature, they cruise the whole reef grazing. so for tangs it is generally recommended to have 6' of horizontal swimming room. (125g + )
C) unless you have a definite back up plan, it is not always so easy to take out a fish, and then move it to someplace that it is wanted. fish stores may not take it, or if they do, give you pennies on the dollar for it, you cant always find a hobbyist or whatever that wants it or has room for it, etc.
D) releasing it into the wild is NOT an option.
E) even a small juvenile tang can get stressed out in a cramped, poor environment. when a tang that carries ick gets stressed, you are guaranteed your whole tank has ick and you may lose all of your fish. which brings up the point of quarantining and hypo
