Ich Infection

Just got a 55 gallon about 2 weeks ago. It has 3 red bellied piranhas as well as a few other tetras. It just came to my attention that my piranhas were acting funny and one of the tetras was carrying what looked to be a protozoan on its side. I added 55 ml of "Rid Ich" and am about to do a partial water change. Also the nitrate was a little high. Any ideas on how to treat this more effectively/ if i should be treating for anything else?

What temp. do you have the tank set at? Bump the heat to around 86 ( will speed the ICH..but also kill off any eggs in the substrate). Add an an airstone for additional oxygen..and I would use some AQ. salt as well. 1 TBSP> per 5 gallons. Since it may take a few treatments to rid the tank completley of the ICH..the salt would be removed with each water change.
I would also treat them for any secondary infections with Maracyn II...once you are thru with the ICH treatments.
Your nitrates will most likely be a bit higher than usual with any med's.
Only way to combat that is with partial water changes....but you don't want to weaken the med.'s either. Just keep an eye on the parameters by checking periodically. Best of luck to you.

Are those real Piranhas. If so, the spot on the tetra could be a bite. I would try to make sure that all the fish are compatible. Of course if you have an ich infection you should treat it like Dizzie recommended.

i have 2 oscars about 7" long with a pleco having trouble keeping water clear

That's because Oscars and plecos like to dig, and they grow to be very large. Of course, it doesn't hurt to check water chemistry every few weeks and, most of all, keep up with the partial water changes.