Wow. Just wow.
To the OP: do your research on ich. Figure out how its life-cycle works and you will see how to kill it. I used the high-temp/salt combo and it worked great for me. Best of luck with your jag.
To the "top off" water-change idiot: one way or another, you're lying. Either you're keeping your fish in much higher nitrates than you're claiming, or you're doing water changes. Even if your water had ZERO nitrates in it from the tap (yeah right), 20% water changes on a 30 ppm nitrate concentration would give your tank about 20-25ppm nitrates AFTER the water change. So, in 6 MONTHS, your fish only poop enough to add 5-10ppm in a 150 gallon tank, eh? 4 Giant Danios, 2 Dats, and 2 Motoro rays? And this supposedly works for your 130 gallon tank with 2 Oscars, 2 Red Hook Silvers, a Royal Clown Knife and a Common Pleco, too? AND your 75 gallon with the Jag and Common Pleco??? I don't care how much you're starving your plecos, they put out more poop than that...and so do the rest of your fish.