[Peter Finke]

I think that a 50 liter-tank is too big for a single pair. They don’t need such a space. I prefer 12 liters or at most 25 liters.
If the tank is too big you risk breeding at a place which you cannot inspect. But the main point is feeding. You cannot feed the young properly. You have to put too much food in it, and that will contaminate the water. Therefore I advise you to take a smaller tank.