Awww really? The pet store I got it from had it in a 10 gal tank.. I asked them if it was ok to have the koi in there and they said yes /: maybe it's a special koi? One that stays small? Darn in payed 20 bucks for that fish...
I think I did get some sort of fantail goldfish! I'll post pics later
Sorry, but there aren't any miniature koi. A few people have claimed to have developed them, but most have been proven wrong. Pet stores keep fish in 10 gallon tanks simply to sell them. They don't have the space and they can't afford to keep 125 gallon tanks up and running. Koi can be kept in small tanks temporarily, but they will grow and they will grow fast. Do a little research and you will quickly find that the minimum tank size recommended for koi is 100 gallons. Koi are meant to be kept in ponds. I'm really sorry, I was hoping that you would see my response, but they really shouldn't be kept in tanks that small.
Fan-tail goldfish can thrive in a 10 gallon tank because they don't have the best swimming capabilities and they stay smaller.
PM me if you have any questions. and if you want a second opinion, post in the BYC Aquarium thread: https://www.backyardchickens.com/t/608356/byc-aquarium-thread/130#post_10844434
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