Goldfish Bowl vs Aquarium
My 5 yr old goldfish has grown too big for his bowl. Would it be better to put him in a 10 gallon unfiltered tank that I will continue to change the water as I have been, or move him to an aquarium by himself?
I certainly don't want to shock him or cause an untimely death, but I know he is swimming on borrowed time in the bowl he's in...we love our Nemo!
You are obviously following the golden rule of goldfish keeping...regular water changes. Goldfish don't normally grow too large for their bowls or live for 5 years in one.
From your comments, I assume the 10 gallon aquarium has other occupants.
You don't mention what type of goldfish you have or size, but if you are considering putting Nemo with other fish, there could be compatibility issues.
Not all goldfish are able to be kept together successfully. Some broad rules would be single tails with single tails, telescopic eyed with telescopic eyed. If any goldfish has an advantage over another, and this includes size, they will get the bulk of the food.
Read more on goldfish compatibility here...
If the other occupants of the aquarium are not goldfish, many tropical fish will nip at the flowing fins of goldfish.
In an unfiltered 10 gallon aquarium, even one 2" goldfish can increase the bio-load of the aquarium quite substantially, so consider what impact Nemo would have on water quality and the frequency of water changes needed.
I haven't mentioned diseases here because Nemo obviously doesn't have any. Moving him to an aquarium with other occupants may put enough stress on the aquarium environment to cause an outbreak, especially during the hot summer months.
Without knowing all the details, my advice would be to give Nemo his own aquarium.