tall tank

So, I have 25 hex tank, it is about 10" on each side and 21" tall. I would say the footprint is about the same as 15 gallon. My ph is 7.4 and hardness about 110 ppm. Currently in the tank I have 8 pygmy corydoras, some cherry shrimp, and various pond and ramshorn snails (who I feed to my...