Hi and Happy Cichlid raising! I have a 75 gallon tank that I am treating for ich. It's weird. I haven't introduced any fish or plants for almost 3 years but one of my guys has ich. He is the largest of the fish and recently lost a couple buddies (2 months ago) due to a severe pH dip. However, I fixed that problem. This is a new one. Dark Shadows has ich. I raised the water temp to 80ish and am now gradually adding salt - 2 tblspns per 5 gal (~ 2 cups) over the course of 48 hours as directed. However, I started to think about what my aquarium looks like when I do a cleaning and remove approx 15 gal of water. It actually looks like it is about 2/3rd's full at that point. So, I am thinking there really isn't 75 gal of water in there. I have about 2.5 - 3 inches of rocks on the bottom and several large rocks and structures in my aquarium. I am thinking there is really more like 50 gal of water in there and that is the number I should use to gauge how much salt to put in. What do you think?