Water quality issues will be your biggest challenge... You will need some sort of filtration system to keep it at a suitable level, even for FHM. As has been stated, they will eat their own fry. FHM are not picky about what they eat and can be fed ground up fish pellets, goldfish flake food or just about any other fish food out there. They spawn on the underside of flat items, so providing these in your container would encourage their spawning. Producing large numbers of them is not going to happen in a 50 gallon barrel. You may be able to keep 30 adult fish under good filtration and transfer their young regularly to another location for grow out of fodder...
