I'm not one to throw the common beliefs out the window, however my corys are group of three, and
extremely active, which is
why they're a trio rather than a proper school of six. I couldn't imagine having school of six in my tank; me, the bettas and the neons, would all go mad.
Also, your mileage may vary in regards to algae wafers for the otos. Some love the stuff and others ignore it forever. Still others just have to '
get used to it' as a source of food and never look back; going so far as ignoring algae in the tank in favour of the wafers, apparently.
Folks will discourage you from buying fish to 'fix the algae problem' and, I think fairly, suggest you alter your feeding and photoperiod to decrease it, instead. Have fun, buy what fits, but also know, otos are notoriously tender fish and die for no good reason. So if you don't' want to add them because you want a cute group of little fish zipping around, reconsider. The diatoms will go away on their own eventually.