They look like young Tilapine, at this age many species look alike, there are almost 100 different species of Tilapines.
Here are some to compare.
Above Oreochromis tanganicae.
Below Coptodon zilli.
below an adult zillii
Below
Oreochromis nilioticus
Tanganicae get a beautiful blue sheen as adults, and grow over 15" long, so will require a long tank (min 6ft) with a sandy bottom and rocky areas to hide in to feel safe, hard water with a pH around 8 is perfect.
Mine grew very quickly in a 100 gallon + tank .
Their natural diet is algae, they are algae scrapers, so pellets like NLS Algaemax , or some other Spirolina/veggie base is best, and allowing a good crop of algae on the decor of the tank is a good idea.
Similar to the algae in this other Tilapine (Alcolapia alcalicus) tank below.