We can't decide what fish to get!

Our main debate is between a Pleco and a Mylandia Lombardoi because they require different PH levels. We are also looking at a blue crayfish. (We also have a 300g, a 250g, and two 55g that they can be moved to when they become bigger) how long could those fish be kept in the 20

Our main debate is between a Pleco and a Mylandia Lombardoi because they require different PH levels. We are also looking at a blue crayfish. (We also have a 300g, a 250g, and two 55g that they can be moved to when they become bigger) how long could those fish be kept in the 20