ummm, a variety. ive tried this so different ways. with flash/without flash, with room lights without, with tank lights, without. without with a strong LED torch. its been trying i can tell you. there are some great tips in the photo lounge. and i think someone (sorry cant remember) posted something about how to shoot great pics in the arowana section but applies for all fish. some people are a natural at it, M|L takes good pics, along with loads of others.
heres one with the LED effect, and with and without flash. makes quite a difference. to be honest i take about 80 bad pics to every good one i get. which is quite poor, considering this fish wasnt even moving!!!