Yes, 5ppm is awesome. It will always grow until you do another change. Water changes every 3 days are keeping it down well for you.
so my only other way is to put some plants?
Dude, have you not read any of the posts? Nitrates at 5ppm is fantastic!
If you still want to obtain 0ppm, then sure, knock yourself out and stick some plants in there
I did im just saying if I want it to be 0ppm is it the only way is to put plants. no ned to be that hastle.