Thanks guys, water parameters are on the 1° post.
I change water yesterday, a big WC, about 50%, today No3 are at the same level... Inside the tank (60L) i have only a Microsorum, Ceratophillum and some floating plants. Dont understand why...
No problem for Gh and Ph i can manage them.
In another 30L tank i have about 0 No3, and the water are the same as the conduction.
Maybe the thickness of the substrate?