seems like no end to this

[pops]

I would up your water changes to 90% or fin level, every time, also keep in mind that even at that you are still leaving some nitrate in the water in the 10 percent left, this also creates a slow nitrate creep, every 3 months or so do a back to back 90% water change to bring your base line back down. 160ppm is not good, looking for reading of between 5 or so after water change to 20 to 35 or just before water change.

 

[squint]

Nitrate creep is a myth we've already debunked here.