Do fins grow back

Yes provided they are given a temperature of 75F, and good conditions as laid down by the rules. :- 1 inch of fish needs a minimum of 1 gallon of water. :- Every tank needs a permanently running cycled filter. :- Every tank needs at least 50% of its water changed every week. Keep the above rules and your fish stand a chance. Fail in any of them and I can guarantee that you will have constant health problems with your fish.