Thanks for your response. Water hardness in my area is 90 ppm in my area. I had no idea about the algae eater, I will look into rehoming him. Frustrating about the knifefish, I specifically told them that I had a 75 gallon tank when I purchased it, but I know they will let me return him to them...
Help! We upgraded from a 33 gallon to a 75 gallon freshwater tank on January 14th and have had multiple fish die since then and 3 more are currently sick. We got the tank from a lady who was giving away her tank and asked that we take and care for her fish. She had GloFish tetras, which she said...