Thing is they are a mud dwelling species. To breed them they need peace away from rock dwelling species. The trick to getting em to breed is to get em to not be bullied by tank mates and to give em some tubes half buried in sand for em to excavate. Bit like the mud tunnels they dig in the wild but in tanks impossible to exactly match. They sure need good water in aquariums but produce huge numbers of young if you give em the right conditions. Not huge tanks required a 4 foot should work fine.
3 is not ideal but could well work with a bit of luck and one male and two females.
Also they are being produced in large numbers by some European breeders so do not expect a huge return on your investment.