Ya know, I think I'll just go ahead and invest in a two gallon tank next payday. I found a vase at home that's a gallon and I will keep him in there for the time being instead of the cramped half gallon.
I'll probably get something with a light too. My bedroom is pretty dark during the day for some reason and I don't always want him in the dark. I'm keeping him in the kitchen for now so he has some light.
Also, we have a LOT of lime in our water. It's the reason why I had to toss my old 2.5 gallon (actually, we gave it to a friend I think). So much lime was on the edges it was impossible to get it off. The lady at Petsmart told me I just may have to replace it every couple of months (the tank was not filtered, btw).
Does bottled spring water or distilled water lack this problem? It'd be worth investing in several gallons of that to keep the lime at bay.
Thanks again everyone for all the help. :)