I appreciate all the advice in advance. Thank you!
I have a 300L tropical tank, I did a standard water test before doing a water change. Nothing was super strange, fairly standard. Nitrate levels were sitting about 10ppm. It was time for a water change anyhow.
The one thing I did different this time though was, before I did a water change I scrubbed with a rough scrubber the algae which had started to accumulate on the side and back glass of the tank. No chemicals or anything, just the scrubber (This scrubber is only used for the tank - never used for anything else). Once done I did a 35-40% water change.
I've let the tank settle for 2 hours then came back and tested the water as I always do. That's when I got the shock of 160+ppm
Nitrate levels! Everything else is fine. I tested 3 times to ensure I didn't do the test wrong etc. Same result.
I then tested the water from the tap, no Nitrate. I tested the water from the hose which the water came from, no Nitrate.
Could this huge spike be cause from the scrubbing of the algae off the glass in the tank?
What should I do? I've already done a fairly large water change, should I do another?