I added another few fish today (at my tank capacity now). Before doing so, my nitrates were at 40ppm so I did a water change and got this down to 10ppm. There was no ammonia or nitrites.
Since I did the water change (around 20%), I planted some plants (anubius, java fern etc) and added 6 neon tetras. All of a sudden i have noticed a slight nitrite spike coming in at 0.25ppm. I don't want my new tetras or indeed existing tank mates to suffer here. Is it possible when I planted the plants that I disturbed the substrate enough to release some decaying food/biomass and this has led
to it? I also planted 2 fertiliser captures in the substrate to help the plants. Not sure of that would have made a difference. Lastly, I added 5 ml of fluvial bacteria booster as it's been a while since I added any and it says to add weekly.
Would another water change sort this? It's the first time since I fishless cycled the tank that I've had a reading showing any nitrites hence why I'm unsure what to do.