Since getting my new fish I've had some water issues. Prior to getting the new fish my water was always perfect. No amonia, no nitrate, no nitrite... The day after I added the severum I did a water test and found that my amonia reading was at 1.5! I immediantly did an 80%-90% water change. I gave it a couple of days and did a a test tonight and I'm still getting an amonia reading. This is very upsetting to me.
Nitrate 5ppm
Nitrite 0ppm
Amonia .75

I added some more Stress Zyme and will do another test late tomorrow. I'm hoping this will do it.

Any other suggestions? I'm still new to this so any advice is appreciated.

Thank you!!

Ok I see you've got an Oscar and the severum. How long have you had the Oscar before getting the Severum? we also need to know what type of filtration you've got, what your tank maintenance routine is, and how you clean your filtration. I'm a little bit suspicious about having a nitrate reading of zero. Keeping nitrate level at zero is virtually impossible because nitrate is a byproduct of ammonia and nitrites, it will be present, especially in the small aquarium. It is possible to reduce it to very low levels but from my experience, the only time you get zero reading of nitrate is when you haven't done the test properly. Most of the liquid tests require that you shake the bottles/vile for a required time. If not, you do get false readings, sometimes zero nitrate.

Your problem could be an an ammonia spike because you've added the extra fish. How big is the Severum? I would suggest that you do a small water change every other day, let's say around 25 to 30%. Stress zyme should certainly help your situation. You might find that everything will settle down in a couple of days when your biological filter catches up with the extra fish

Ok..
I've had the Oscar for approx. 2 months. For filtration I have a marineland C-360 cannister. My routine so far has been a 25% water change every week. I have rinsed out the media once so far in tank water. I have the API testing kit and followed the instructions for testing to a T. I can do the nitrate test again today though and see if the results are the same.
The severum is quite small, an inch probably.
I will go ahead and do another water change of 30% today.

Thanks for the advice. I'll let you know what happens.

Tt is impossible to get ammonia and nitrite and nitrate to all be 0 after 2 months. My guess is that at least one of the results were wrong

If the last set of tests were right then i am guessing that your filter is playing catch up. Before you added the new fish the amount of good bacteria in your filter was in balance with the fish in the tank. When you added the new fish you added to the aqmount of ammonia produced and there wasnt enough good bacteria to process it. It shouldnt take too long to catch up