In my little betta tank with a big ozelot sword and a lot of floating pennywort, it did stop recurring cyano
but didn't help with nitrates.
Then the filter died. Then I did see a huge drop in nitrates. After a few weeks with no water changes it was zero across the board.
Makes me want to start fresh with a new tank, pack it with plants first, then start a fishless cycle ... The idea being that the plants suck up ammonia and it never becomes nitrite or nitrate ... And the beneficial bacteria only establish enough to get the ammonia the plants can't handle.
I could be completely misunderstanding the whole thing but it was interesting to me that plants helped most after the filter quit, and the tank is healthier without the filter.
Sent from my iPhone with three hands tied behind my back.