I should have specified that the koi are indoors because we've had negative temps outside and I can't keep the pond from freezing. I have a 6000gal outdoor water feature that my koi stay in when it's above 50*F.
I have them in the 55gal as a hospital tank. When I bring them inside, normally...
Size of aquarium/pond - 55gal
Types of fish - koi
Number of fish and sizes - five 5-8 inch
Filtration used and how do you clean it and how often - aqueon 55/75 and aquaclear's 55+ gallon filter (not sure model #), cleaned once a week
How much in the way of water changes and how often --...