I have a 15 gal hex. I did a fish in cycle before learning all about it. I thought my cycle was finally finished because my readings were 0 or (or .25) on ammonia and nitrites, and probably 3 on nitrates. I’ve had it set up since early Jan. I have 1 betta that was introduced in early to mid Jan, a Pygmy Cory that was added last Saturday, and an anubias nano installed on Monday. I have a penguin bio wheel 125 filter. It has disposable filters, but I’ve never replaced it or even rinsed the one that’s in there. I checked my water using my api master test kit last night and my ammonia is at 1! (It has been 2 days since I had tested before, and it was .25 or less then). I changed 30% of the water, and this morning I tested again. I’m still at 1! No idea how that would happen. Maybe my tank wasn’t finished cycling? Nitrites are still at 0. Ph is 6.8. Temp is 81. Should I look into a different filter? I feel like my tank isn’t stocked enough to cause a spike like that. Maybe I don’t understand this as well as I thought I did! Oh, I should add that I added 30 drops of prime after my water change, and I do use aquarium salt, carefully measured, with the proper amount for the new water only.