Tiger barbs are far too active swimmers for a 5g...and too large as previously mentioned. A school of tiger barbs needs a tank with at least 30-36" of swimming space, IMO.
My best advice is go to http://www.franksaquarium.com/nanofish.htm. They have losts of micro freshwater fishies.
I suggest you make a list of likely fish and who and how many can live with who if a mix is desired, plus info about how they live, difficulty rating, etc., and let him pick and choose if he is that type of person. Go to the pet/fish store together to select likely fish. That way he can also see how they live. If he likes to do carpentry, for example, maybe he would like to research aquariums and weights and such and make his own tank table. If he's on the net, tell him about this fine site; if he's not on the net but is looking for an excuse to learn how to use it, researching aquarium fish might be the excuse he needs.
Sounds like a great Father/child project! Let us know how it goes.
my suggestion is to get maybe neon tetras. They're small, you can put maybe 6 - 10 in there if youre' lucky, with a kuhli loach for clean up and pleco that doesn't get more than 3 in.
my suggestion is to get maybe neon tetras. They're small, you can put maybe 6 - 10 in there if youre' lucky, with a kuhli loach for clean up and pleco that doesn't get more than 3 in.