Tank?

Hi! When I got Bubbles, he was in a 1.7 gal tank. I know if there are any experienced goldfish keepers on here then they will absolutely die when they here this because "it is just so cruel!". I know it's probably not big enough, so the night I got him I set up my 5 gal tank. Yes, I know many goldfish keepers are still going nuts. I will get him a bigger tank if I need to, but this fish is almost nine months old and has lived in a 1.7 gal tank for its life, so it may already be stunted. I don't know but I will get a bigger tank if and when I need to. But Bubbles has been in his 1.7 gal tank for at least six months and it was not my fault, but he is doing just fine. He's about two inches long, and doesn't have all that much room to race around his tank, but he's got enough. I'm putting him in his 5 gal fish tank tomorrow (after aerating it for three days) and I will have both filter systems in this tank. One is an under-gravel filter and it came with the under-gravel filter. The other filter is one that sticks to the side of the tank and came with the tank he is in now. I do plan to put both filter systems in there. I have a few decorations to put in one corner of the tank and the rest will be let open swimming space. I'm thinking this should be okay for him at least for now. His 1.7 gal is def too small and I know people will probably get mad at me for this post, but I don't have access to a bigger tank at the moment. So here's my plan:
"Five gallons, with an under-gravel filtration system and another side-cling filtration system. I will decorate one corner of his tank so he can hide, and then leave at least 3/4ths of it open swimming space. I will keep feeding to a minimum to avoid over-feeding too badly."

I know probably nobody reads my blog, but if you do please comment and leave your constructive critisism. Don't worry, I've loked at hundreds of websites and heard other people being chewed-out for keeping their goldfish in smaller tanks, but I only have access to the 5 gal right now.

  Thanks for any help you might have,
xoxo Em