I keep minnows in a 15 gallon bucket all the time. All I have is a large air stone and aquarium air pump and a filter to keep the water kleen. If you plan to keep them for a while, just a little gold fish food like the last reply stated. Also in warmer weather I keep 2 litre bottles filled with water and freeze them and keep one in the bucket to help keep them cool. If they get hot they will die very fast. Good luck.