The clownknife fish are one of the coolest fish that I have ever owned. If you are serious about keeping one of these fish then I suggest that you try to get a royal clownknife. They get the same size and are just aggressive but the only difference between the two is instead of having spots they have what appear to be stripes going down the sides. As for as tank size I would reccommend tanks 75gal or bigger. They are nocturnal fish but everyone that I ever owned would swim around just fine with the lights on. I fed mine raw shrimp, bloodworms, and brine shrimp occasionally I will feed them feeder fish and raw meat. I had fake plants, gravel substrate, driftwood, a pleco, and a tire track eel with mine. The only reason I do not have mine anymore is because he out grew my tank. I had a 16" clownknife is a 40gal. long. If you would like some more info pm and i will tell you anything you need to know.