Yellow labs are one of the least aggressive african cichlids, not to say they wont put up with tiger barbs nipping them...I dont think its a good idea for the barbs, unless your tank is very large (75 gallons or larger)............You can acclimitize the barbs to your african tank by putting them in a small tank and slowly raising the Ph in there tank till it matches your african tank....Dont raise the Ph alot in a single time.........This could take weeks to do, but has worked for other people i know............If you do this, make sure you get at least 6 barbs, any less than that they become real fin nippers