Again, thanks for the prompt reply. I have one kit I cannot remember the name of, but the other one is API for nitrate. I tested my tap water and aquarium water-both same very light blue colour after 5 minutes. I even left it for longer, did not make any difference. I have the original Juwell internal filter with different colour sponges. Some of them should be getting rid of nitrate, but they can't be that efficient. I replaced them in August.
I only have artificial plants and two airstones that are on for a couple of hours/day.
I only have artificial plants and two airstones that are on for a couple of hours/day.