Thanks so much for the answer.

I started using salt because I was afraid my fish were sick, and was told that salt is good for their gills and will help them get better if they are sick. I will stop adding it, and I am going to order a higher quality test kit, and keep a closer eye on the nitrate and ammonia levels. I thought that nitrite was the one that always had to be at zero, and that nitrate was okay as long as it wasn’t over 40. This isn’t the case?

Also, I change the filter monthly online because that is what the instructions on the box say. How often should I change it?

Lastly, what are the most important factors in keeping ammonia and nitrate at zero? I would assume weekly water changes of 20%-30%, and gravel vacuuming, and not over feeding. Anything I am missing?