Woah, chill. Even with a 55 that fish will only live in there well for 4-8 months depending on how big he was when purchased. At 10" I'd say a bigger tank will be needed. I don't think this is the best choice as eventually the pet shop will get stuck with an aro in a 30 gallon. I'd recommend saving up the money until you can afford at least a 125 and then get your aro. A big pond is also an option.

