65 gallon tall. It's understocked until you count in the two plecos I have in there for now. They're pigs. Other fish are pygmy corydoras (down to just 2 or even 1 now), galaxy Rasbora's (down to 1!), a school of 4 mosquito fish, one black skirt tetra, two 4-5" common plecos, and my tire track eel. I've had some south American cichlids in there when I remember my pH being lower. And I wanted to add some again. But I can't until I figure this out. Anyways, I just tested my water to be sure. pH is higher than I remember (actually haven't tested this for a couple of years) at about 7.5. I'd like to figure this out. My Ammonia is .25 ppm (I'm behind), Nitrite is 0, and Nitrate is weird at 40-80. They look the same on the pamphlet. It's API. Actually, I don't remember if you're supposed to compare the test tube with it laying flat, or standing up. Bc the nitrate is darker standing up. I'm noticing the deaths following fertilizing the tank. I'm doing the estimative index https://www.aquariacentral.com/forums/threads/co2-fertilization-algae-and-more-updated-10-10.136668/. But actually, I'm dosing less amount (only 1/4 tsp all combined) and only 2x per week. Because I can't keep up with water changes several times a week. I can only manage 1-2 per week. I have T-8 lights that came with the tank, which is low. I haven't changed them out yet. I'm going for heavily plants. So far I have some vallisneria, cocombia, Java mass, Java ferns, and a couple of other things. I use the SAME ferts method in my other two tanks, including with a shrimp, and no problems. I also used the same when I used to have a lot more tanks. What's going on? Please help me figure this out.