I have all males right now (4 of them) in a 40b with 6 bolivian rams, 2 peacock gudgeons, 6 panda cories, 6 or so neon tetras that are descendants of the original 20 I had, a bumblebee goby, a trillion MTS, and half a trillion ramshorn snails. I USED to have 8 female flags in there too, but I moved them. The males seem to be getting along with other tankmates and each other just fine, now that there are no females to compete for. I wouldn't call them aggressive at all. EXCEPT when they are guarding their eggs. THEN they are holy terrors and no other fish will be able to get near their nest. Period.
So, if you need bba gone or hair algae, these little critters will do the trick. Keep in mind though, that they don't discriminate between algae and tender shoots and soft tasty plants. As I said above, the 30+ water lettuce I had in this tank slowly shrank to nothing over the course of 3-4 months. They also nibble on vesuvius, duckweed and salvia. Hardier plants like bacopa, sag, crypts, java ferns - no interest.