Idea for an algae "farm" for my Mollies. Could use some info.?

i cannot add anything more to the advice from the first answerer, but i can mention that your mollies would be just fine in your tetra tank, even if it is just for a short period of algae maintenance. Put two or three in there so they chase each other around and not the tetras. Mollies to ok in soft acidic water and do not have to be in brakish water.