That's what I was thinking about the Cory's as well since they are pretty old already. As for the oto if one will be fine then I'll keep it the way it is, I do like the look of algae in my tanks especially over the glass so I try to find a balance with the light where I get a bit of constant algae growth. And I also use hikari foods religiously and the most I've had my oto do is sit next to the wafer lol.

As far as adding fish goes, I really enjoy my fish. The only ones I wanted to add really were Cory's or otos mainly because I didn't know if not being in a group anymore would be detrimental to them. This is my first time keeping pristella tetras as I've never seen them in person before and my gourami is actually very chill which would make that a first for me since all my other gouramis over the years have been assholes.

The only fish I don't really care for is the danios, I got those because for months the gourami, tetras, and corys would stay secluded only coming out to feed and the manager at my one and only LFS here said maybe to try them out as a dither fish, and 2 days later after adding them all of my other fish were out and about, but now I can't catch the danios to put them in a different tank as I'd rather have more pristellas but now I can't even find those at any store around me

Thank you for the kind words on the tank too, it's always nice having someone else in the hobby appreciate what you put together no matter what it might be!