How do you ensure your pH is stable?
What filtration are you using?
I am hoping u won't say u undergravel.
Excess nitrate peaks generally are due to over feeding with excess waste build up in your filter which then leads to sudden peaks. If you have a planted tank u should be ok. But judging from what you have said I really feel you should look into the feeding issue.
Also if you don't have a decent canister filter now would be the time to get one.
I have a 500L discus tank and have managed to bring down my WC
's to just one 20-30% per week and I only do this because its a habit. I can honestly say I don't need a WC
for a solid month with zero problems.
I'm using a Fluval FX5 canister
A Biolife Clip-on
My media :
I seed using either Stability or Microbe Lift