pic looks ace, yea the mollie and the platy would still go for the algae wafer, they used to eat the catfish pelets as the were falling, funny to watch, but not for the loach who died
Bristlenose Catfish ideally need a minimum of 15G as they can reach about 5" and produce a lot of waste.
As others have said, Pitbull Plecs should be ok provided they are in a small group and the water is well oxygenated.