May be the most common, but I still prefer the black convicts over the pink or various marbled types. If you breeding them to sell though you wont make much if any $$$ whatever way you go, but will have better luck offloading them with anything other than the common black stripe.
Yours is a 20 tall it can still be done I just personally think they do better in 20 long. You will want at least a couple caves in there for them (they will breed either way, but convicts are less stressed with a cave to hide in). Few more rocks to make natural caves or even few pieces of pvc would be good in my opinion.