Be very careful with that cichlid. The Blue Cobalt Cichlid (Metriaclima callainos) can become quite aggressive to the other fish. This one is from Lake Malawi in Africa and prefers harder water with higher ph - just a FYI. It should be fine in a 60G but still might pick on the others. I would prefer to have these in a Lake Malawi tank only - but that is my $0.02.
Definately move him as soon as possible.
As for algae - test for Nitrates(NO3) and Phosphate (PO4). If you dont have tests - take it to LFS and have them test. An imbalance of nutrients will cause algae very quickly.
Once you move those fish - a pleco will fit I would think (or some otos at least). Currently, I would say you are at max or past max. I am surprised that cichlid is not picking on everyone - is it a female (they tend to be less aggressive ime).
idk if its male or female but it is pretty passive it never picks on ne of the other fish in the tank once i get all the fish moved i plan on planting the tank with some mollies or tetras and some ottos and ghost shrimp