So I have a 240L tank with a variety of different fish. I have a fully grown common plec, 3 clown loaches, 2 Angels (1 marble, 1 platinum), 2 Cory catfish, 1 upside down catfish, 4 Bala sharks, 2 pearl gouramis, 3 cherry barbs and 2 shrimp I have no idea what species they are but they’re fairly big and just live under a rock. My tank is pretty much perfect in terms of nitrate, nitrite, pH and all of that apart from general hardness which i don’t know how to get down. I was thrown in the deep end a bit as the tank wasn’t originally mine, and now it’s been in my care since Feb, so I’m still quite new. My predicament is, I want more fish (cichlids or a single oscar but I know that’s a stretch) but I just don’t know if I should get a new species of fish or add to any existing ones. Thanks for any help!