This is a pretty weird situation that I'm in...
As most veteran forum members here know, two of my turtles, Hurricane and Typhoon have shared a tank their entire lives. Not ideal, and I'd like to separate them, or at the very least upgrade their aquarium from a 55 gallon to a 100 gallon sometime soon. The reason I'm bringing that up is because I thought that the two of them sharing a 55 gallon was why I couldn't get control of the nitrates. Just too much turtle feces, too much urine, too much bacteria, etc. However, this problem didn't start until after I moved to my new apartment last year in September. So I don't think their feces are the problem, especially since I clean their tank of that regularly. They get regular water changes, as well.
My third turtle, Sadie, has her own tank. She is a HUGE RES and she goes to the bathroom constantly. Keeping her tank clean is a lot harder than the other two. I have had no problems with her tank getting outrageously cloudy.
They all have the same diet, and the same filter in each tank, the Cascade 600. Both filters are around 3 months old.
I prefer the Cascade brand, because for dealing with nitrates it has always been a huge help. And in Sadie's tank, it is a huge help. But for some reason the nitrates in Hurricane and Typhoon's tank keep building up. I've been doing the nitrogen cycle the way it's supposed to be done. I treat it like a very delicate process, because it is, and now all of a sudden after 11 years of doing it right, it won't work??? I am painfully confused.
I completely restarted the cycle, emptied all the water, did a 10% water change every day, and the tank would NOT stop getting cloudy. I went as far as to use my super old method of treating the water with a tablespoon of sea salt to treat it, and increased the percentage of my water changes. Thinking that maybe there's something in the tap water at my new apartment, I even made a few gallons of sterile water, waited for it to cool down and added it to the tank, and that made zero difference. Finally, getting totally fed up with this nonsense, I did the one thing we all tell ourselves we shouldn't do: I took out most of the water and replaced it with straight tap water. The tank is VERY clear today. Previously, after any major water change, the tank would cloud up overnight.
I'm glad the tank isn't cloudy anymore, but without knowing the cause, I have no idea how to prevent this in the future. Any ideas/suggestions? I'm open to just about anything.