Heres a photography technique that Cristie Van Zyl from Cape Koi Aquarium taught me a year or two ago.

1. Bowl the koi. Take the bowl and put it on a table or on the floor.
2. Make sure that all the fins of the koi are covered with water.
3. Throw a towl or piece of cardboard over the bowl so that the complete bowl is covered. Give the koi 1-2min to relax.
4. Ask someone to lift the towl or cardboard slightly while you peek in with the camera.
5. Have the flash on and camera on fast shutter speed or ISO 200.
6. Wait for the koi to swim towards you.
7. Wait for it to fan its pectoral fins out nicly while keeping its body straight.
8. Aim the focus just infront of the dorsal fin.
9. Make sure your angle is not to shallow and SHOOT.

Check the photos before releasing the koi.

Ja Wayne