Can I raise Koi in an aquarium?
  Koi can be kept in aquariums as well as ponds. Aquariums need good filtration and aeration systems. A filter utilizing carbon is recommended for aquariums. Use a chloramine remover whenever adding fresh tap water. Most cities have chloramine in their tap water. Periodically clean the filter. Most filters should be cleaned at least twice a year even though the water looks clear. There is no such thing as a filter that never needs to be cleaned! When transporting Koi to an aquarium or after a long trip, float the bag for at least an hour before releasing the Koi.