FANTAILZ:....microbelift makes a good BROAD SPECTRUM antibacterial food...amongst others.
LARKIN:....green peas are an oldschool treatment...I googled "green peas and koi" and posted a little bit of documentation for you, here:
Heres a copy and paste from the article "Feeding vegetables" from AQUATIC COMMUNITY:
****If you fish are prone to constipation, try giving them boiled green peas. A lot of goldfish breeders regularly feed their fish boiled green peas since the compressed and heavily altered goldfish has compressed intestines that easily clog up without sufficient amounts of fibre. Boiled green peas have saved the life of many a goldfish. Boiled snow peas are also popular but should be split prior to serving
****This is a segment, cut and pasted from the article "Bouyancy Problems" on petplace.com:
Green Pea Treatment
Oddly enough, one treatment that has had good results is feeding your fish a pea. That's right, a single green pea (canned or cooked and lightly crushed) once daily often helps cure the problem. Exactly how the "green pea" treatment works is unknown, but it is possible that the pea helps move or displace lighter and/or air-filled food through the digestive tract. Your veterinarian should still examine your fish, including a physical examination and radiography; however, the harmless and inexpensive "pea treatment" seems to have its place in managing buoyancy problems of goldfish.
The "green pea" protocol should also include increasing the water temperature to 75 to 80 degrees Fahrenheit and continued feeding of the regular commercial fish food. However, discontinue feeding your fish floating pellets or flake