I figured out why the melafix isn't doing anything... The dosing instructions said 1/4 capful for 600 gallons, which I was following, but then I eventually noticed that it said 1/4 capful (60ml) for 600g, and I knew that wasn't a 240ml cap... Now I've started to use the measuring cup to measure out about 30-35 ml to dose instead. Hopefully I'll see some improvements within the next couple weeks. Will keep the thread updated.