Weekly partial water change is the best way to control the NO3
If you are willing to add plant to the tank, that would be even better, but do consider that you need add additional items such as proper lighting and maybe CO2
In fact, issue with most planted tank is not enough NO3
Btw, your fish would be fine in the tank with moderater NO3
as long as there is no huge fluctuation in any water parameter (pH, temp, NH4
). Its the fluctutation that kill the fish most of the time.