Oh ok I understand that, but what about phosphates?Thalas_shaya said:You should have Nitrite and Nitrate tests already, assuming you have a basic test kit. That's your nitrogen levels. API, Seachem, and Salifert all make phosphate test kits and are trusted names. Test kits are less convenient than strips, but my experience with strips is that they're not reliable. They work great if they're pristine and uncontaminated and not expired, but usually one of those things has gone wrong.
Also, in short, plants do help keep nitrate down, but it takes a significant quantity of plants to get significant nitrate reduction.