My 40l Empty Tank

[Paradise_2]

i have taken back the koi and now i have been looking at getting a betta. What do you guys think i shud do?

 

[Paradise_2]

Oh yea its not a betta its a bubble eye goldfish i want

 

[Tokis-Phoenix]

Minimum amount of recommended gallons for a fancy goldfish is a 20gallon long tank, 40litres is about 10 US gallons, so you would only be able to keep a bubble eye goldfish in such a tank in the short term before eventually upgrading its tank to at least a 20-30gallon long tank (i'd recommend a 30gal as that way you'd be able to keep 2-3 fancy goldfish, as goldfish enjoy the company of their own kind a lot).
Bubble eye goldfish don't grow as large as a lot of other fancy varieties of goldfish, they are one of the smaller varieties of goldfish, most only grow to 5inches long maximum, so i would say you could keep an absolute maximum of 4 in a well filtered 30gallon long tank or 3 in a 20gal long well filtered tank- however a 10gal is too small for even one in the long run as it simply doesn't offer enough space. There must be no sharp decor in the tank so they don't damage their eyes on anything, if you opt for plants, i'd recommend silk ones instead of plastic as these are safer with such goldfish. Live plants may be eaten by the goldfish.
Pics of colour varieties of bubble eye goldfish;

http/www.bristol-aquarists.org.uk/goldfi...bble/bubble.htm

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edit: I would just like to add that because bubble eye goldfish are one of the smallest growing varieties of fancy goldfish, this is why you can get away with one more than you usually would be able to with fancy goldfish stocking and minimum amount of gallons etc depending on the situation/circumstances. Usually it is 20gals for the first fancy and 10 for every one after that. Goldfish tanks do best when over-filtered as goldfish are big waste producing fish.

 

[Paradise_2]

Either way i think i will still get one anyway as the variations i have seen look like a common goldfish but with the bubble eyes, i think they are a unique variation of the telescope goldfish