Strange Water Readings

[sean0151]

Hi Folks

A couple of days ago i did a 50% water change a thourough gravel vac and some cleaning of stones( in tank water).The nitrate readings had been showing 40>80 ppm using my liquid api test kit,yesterday i tested water again and readings were still 40>80 so did another 50% water change with no gravel vac,i tested again this afternoon and readings are still 40>80.So just to verify test i tested my tap water which shows 40>80 ppm.strange.
I have an old but indate nutrafin test kit so i tested using this and got readings of >10 ppm.
My faith has always been with the api kit after the nutrafin let me down once but i now dont know what to believe.

All other eadings are fine using both kits
ammonia 0
nitrite 0
And ph and kh as always
It is a 600ltr tank which has been cycled for about 9 months and has always been stable.
Filter is a fluval fx5.
Any advice or opinions

Thanks Folks
sean

 

[dayzofspeed]

if your tap water is showing 40 - 80ppm then i dont think you can get it lower, and besides that amount isnt disasterous anyway