Nitrate spike?

[GreenSpottedPuffer]

Yeah maybe the gobies I was thinking. They are awesome by the way when they actually come out of hiding.

I have a high bio load, so I expect nitrates but this was very sudden. I test quite often and always got 0 but then suddenly 10 the other day. I have done a few water changes and will test again today.

The sps look fine still but I doubt they will like it long term.