How?

[Thatfishfreak91]

I did I fifty percent water change yesterday to lower ammonia and when I tested it today it was at 0.5 which was lower BUT my nitrate went up! My nitrate is at 10 ppm and nitrite is at 0 ppm

 

[Mebbid]

It's possible that there are nitrates in your tap water. What was the nitrate reading before the water change?