What is going on??

[Vader6]

When I got my Lemon Pastel I put her in a 20g tank. She didn't eat for about 3 weeks due to this. I switched her to a small tub, waited 5 days, offered food and she took it right away. Move him to a tub, it'll only cost about $15 at the most. And it'll fix your humidity.

Thing is I spent around 180 on crap for the tank......what am I going to do with it now if I just ditch it?
If I were to get a tub how would I set it up?
I don't have a rack so just get a 5 gallon UTH and put in on the bottom of it with a hide on 1 side and a water bowl on the other? Poke holes in it for air and put aspen down for bedding?
I just got my therostat in so I'm good with that now.
Let's do say I put him in a 6 qt tub for a month then upgrade him to a 15 for another few months, could I put him back in the 20 gallon after that?? I mean I have all the stuff......
Don't get me wrong I want my little guy to eat it's just I don't want waste money. I'm a poor college kid and throwing 200+ bucks worth of reptile supplies and tank out the window seems wasteful. So in like 3 months could I switch it back to the 20G.