labs should be kept as one male specimen with other mbuna or ideally in a group of 1 male, 2 or 3 females.
how long is your tank ? generally, for Malawis generally, and in particular Mbuna (a specific grouping of Malawis, of which yellow labidochromis caereulus - yellow labs - are part), you want at least 3 foot long set-up and to be honest the best advice is 4 feet.
if you don't, and you probably don't, have the greatest tank for Malawis, there is a pretty good selection of Tanganyikan (tanganyika is another rift lake) Cichlids which could be combined in there; any of them available locally ? equally a pair of Jewels and some community fish would be nice, or Rams, or Apistogramma species.