Don't bother with salt! I never found a difference for oscars!
I had 16 oscars at one time, so I'm speaking from experience, but not an expert! I never medicated ANY until this year, when my 2 year old oscar got sick, my idiocy, dun ask!
Anyways, back to you! Highest I've went wuz 84, but I always stay 82! Add an airstone like Juice says!
I usually feed cut up market shrimp (I just cut small pieces with scissors) $6 bux at T&T for frozen market shrimps, they seem to like it way more than pellets, and it doesn't get the water dirty!
As for Omnipur.. my oscar got sick twice, used it twice, always fix everything back up in 2 days, even his fins.. i had something like fungus that rot up his fins! one treatment wuz all it took for my wifey's lil baby!
Anyways, good luck! btw, try to spread small meals throughout the whole day, I jsut find that all fish do better, or maybe it's just me =) Good luck!