I read once that it hasn't been proven that the presence of carbon in the filters (throughout the fish's whole life) can cause HITH, but introduction of carbon (midway throught the fish's life) can. I agree, 50% bi-monthly isn't enough, more like 50%/week. Also, what size tank is your oscar in? Two 75 gallon filters is irrelevant if it's a 300 gallon tank.
Edit: nevermind, I just reread your first post (reason #1 for careful spelling). Isn't a 75 a little small for an oscar and a severum?
Edit: nevermind, I just reread your first post (reason #1 for careful spelling). Isn't a 75 a little small for an oscar and a severum?
