Dats a goldfish. Looks like a fairly young Ryukin.
It needs 30gallons and double filtering (a filter rated to 60 or more gallons). For each additional goldfish add 15 more gallons to the tank size and double the filter (ie: 2 goldfish, 45 gallon tank, 90 gallon filter).
Goldfish are very messy and produce a lot of waste. They can also live to 20+ years if they are cared for properly.
Roan