Certainly no flames from me, ChileRelleno.
I just wanted to add that behavior is just as important as size when considering the space that you're going to give a fish. For something that is sedentary, like a freshwater Wolf Fish, a tank of 1.5 times the fish' length wide, and 5 times the fish' length is enough space to observe their behavior w/o endangering the fish. Wolfs are pure ambush predators, who wait amongst clumps of dense vegetation in slow waters for meals to come by.
An African Tiger Fish, on the other hand, is built like a saltwater Bluefish (Pomatomus saltatrix). ATFs come from fast flowing river environments and are built for speed over distance with their elongate compressed bodies and deeply forked tails. Even a tank 10 times as long as the fish' length and 2 times as wide as the fish is likely to result in plenty of crashes into the tank walls, and the secondary infections which often ensue from the injuries.
Visualy it is a stunning fish, but housing one...