My tank is a FOWLR and it has been running for about 6 months now. After my cycle and numbers were at 0 everything was good till about 3 months ago I had a slight spike that went up to 15 or so and I found out I was overfeeding them causing this. After weekly water changes and twice a day feeding instead of once I brought my nitrate down to 0. It was good for about a month or 2 and now it has slowly started going back up and is at 10 now. Nothing has changed other than I had 2 new fish but 1 died and removed it within a few hours of it dying cause my HC's were starting to eat it. Are these nitrate spikes normal?