while i agree that the tank is definatley an improvement on the goldies previous home, it's not really suitable for the fish long term.
It's like taking a great dane from the v small cage he'd been living in, and taking him to a 1 bedroom flat with no garden.... it may be better but that still doesn't mean it's good enough
i'm sorry if we're coming off harsh here, i really hope this doesn't discourage you from fishkeeping, however a lot of fish fanatics get quite upset about the poor deal that goldies get in life.
my personal recommendation would be to donate the goldfish to someone who has a pond so he has somewhere suitable to live out the rest of his life. do a fishless cycle on the tank to set it up properly for fish, then stock it with some fish that are suitable. There's loads of pretty tropicals that you could keep and your conscience would then be clear that all the animals in your care have a suitable home.
Because of the bubbles you get in the tank for a few days when you first set the tank up, I wouldn't add the goldfish straight away.
bubbles don't harm the fish though! it's just oxygen, the fish won't care in the slightest!
i have a neighbour across the road and her goldfish outside in the pond are like giants so i suppose i could ask her if she wants nemo but than what fish should i get and how many also whats the diference between coldwater and tropical and what do i do then as i will have to convince my 7year old that nemos gonna be happy across the road if the neighbour agrees