First of all, I just recently got back from a week long vacation to find that my auto feeder had somehow broken and released ALL of the food into the tank. When i got back i imediately changed 100% of the water and cleened the gravel of all the food. I have carried out 25% water changes daily and treated the water with stability, prime, and ammo lock. My most recent water test was this: ammonia: 3.0 nitrite:1.0 nitrate: 20.
I dont know what else to do. My oscar is eating fine and acting very energetic. However, his tail keeps getting rips in it. Once one rip heals another is in its place.
Any advice would be greatly aprecciated.

There a good chance you have messed up your cycle in the filter. the only real answer is to keep doing the water changes and testing as you have been doing. what size tank and stock are we talking about also what filter do you have.

adding prime or cycle after the water change is good. But its vital not to let ammonia,nitrites get any higher. your fish will suffer if not straight away this will be long term damage to gills etc.

marcus has the key to the lock...........

It apears that my ammonia is decreasing now. However my nitites are still the same and still too high.

yes, rotting fin is a sign of bad water condition. what testing kit
do you have? strip? liquid?
your fish should be breathing heavily (gasping) i suggest you do 50% water change without touching the filtering system.

I use strips which i know is not the best choice but i just dont have the money right now for the liquid tests. Anyways i did a 50% water change today as suggested. My Oscar seems to be doing much better. His fins arer healed and hes not gasping. (never really did though). I will continue partial changes daily until i can get to my lfs for a water test.

its good that the ammonia has dropped and I think you will notice now the nitrites will drop too. ammonia turns into nitrites when broken down.so cos the ammonia was high its turning point will raise nitrites, you will find your nitrates will be high too after a few days as the nitrites turn to to them.

the fact the ammonia is dropping shows your filter wasn't badly damaged and has regained control. but please keep check to make sure. if it dose rise again you can stop or lessen the feeding. and do more water change. sorry its a lot of water changing but its the only way.