Ross, personally I would check craigs' list and garage sales for a used tank, or better yet, construct one yourself !
A 90 is nice, but really high sides, and unless you have long arms, this will be quite a chore to keep clean weekly, and daily.
You need minimum this for an adult:
36" x 18 " x 18.
Most of us use a constructed 48" x 24" x 24, this will give them lots of room for their whole life. I personally am constructing a stacking duel enclosure on a storage base for my two babies. The older one is handicapable with only 3 feetsies, so I converted a china cabinet (37" long x 41" high) with two levels, two uvbs, and spot lamps with a gradual ramp for him. He mainly stays on the top level, made like the battlements of a castle, so I don't worry about turning on the bottom lights and heat.
Since yours and my younger two are so small, you really don't want to overwhelm them with a whole lot of space, so I am trying to get mine done so by the time they are a foot in length, they will be moved into their permanent enclosures.
Janie.