As has been stated, glo fish are genetically modified danios and tetras that are used for both scientific and commercial purposes. They're essentially identical to their unmodified counterparts and as such the danios will need no less than two feet of lateral space to swim in, giving you the 20 long and 29 gallon tanks as solid choices for them. They'll prefer a bit of a current to play in, and an airstone will delight them. I find them more attractive under natural light (then again I also prefer natural danios), but children may enjoy them under the blacklight. I find claims of health risks from the glo light dubious, but it may be worthwhile to have a normal led strip as well as the blacklight if you choose to go that route, as a blacklight doesn't look very good in daylight.
My opinion, however, is that given the investment required to properly house danios, it would be a shame to limit yourself to a species tank when you could possibly find even more entertainment in naturally colorful species.
My opinion, however, is that given the investment required to properly house danios, it would be a shame to limit yourself to a species tank when you could possibly find even more entertainment in naturally colorful species.