Hello Camacho. I don't see a problem going back and forth from Prime to Amquel +. Too, I would recommend getting an
API (liquid) Master
test kit as test strips can be inaccurate and not as reliable. However, when using Amquel + you may still get a reading of ammonia present during the first 24 hours of using it but it won't be toxic to your fish, (when using the API liquid test).
Personally I would like to see a bit more filtration on your tank. Are you using
activated carbon? If not I recommend adding some and see if you can tell a difference. Three months is a long time for an algae bloom.
Best of luck and keep us posted.
Ken