It's pretty serious, there is an article there explaining the method, it's simple actually. As far as why, I think it's just a gimmick for the cafe the guy is running. Nice stuff, though I dont know if I would use those fish, I would use huge shoals of tetras and stuff. As much as I love the cichlids he's using, the effect is lost by having single fish swim here and there. Huge shoals of colourful tetras would make a much bigger impact, IMHO.