Make sure you have 2 females and 1 male only or the single female will get killed... Also a tank size of more than 30 gallons is recommended for a breeding pair, however if a pair forms in the tank soon, remove the other convict from the tank and it should all be good... Aswell... you said brown algea? you really don't need any bottom dwelers to clean this, ottos are small and may get killed by the convicts (don't know for sure on that one, never kept them together) do a few water changes (should stimulate mating) and just wipe the algea away with a cloth (sterilized!) and it should be good.