55 gal. fish tank set up

Question
Dave, this is a follow up question to our prior conversation. We got the tank set up completey, but my husband came home with two Koi fish instead of tropical fish, so we put them in the tank and thay seem to be doing fine. I didn't put a heater cause the water temp has been at 70 degrees for the last week. I put stress stym and bactrium in the water, no salt should I add some? Please give me any helpful info you can about caring for Koi fish, like what food? Also where can I got 1 new Bio-wheel right, do you have any suggestions on where to purchase 1 more not so high priced. This one was 16.99 at local pet store. Thanks so much for your help, it is greatly appreciated.

Answer
Most fish stores should carry your bio-wheel but I would not replace the wheel itself unless it is literally falling apart.  Feed the koi flake food and small pellets and also three times a week offer them one-two cubes of frozen brine shrimp per week.  dave