how long after to get an accurate test reading

[debaric]

nutrients have not been as high as i want them this week. How long after adding nitrogen and phosphorous would i get an accurate test result telling me exactly how much is dissolved in the water column? I notice that when i dose i see a whitish film over the surface of the water, so this is why I ask.

[tanker]

I would wait till that night or next day.

Whitish film?? Oils of some kind...are you sure it is from the dosing??

[Mgamer20o0]

should only need 20-30 mins more so if you put it in a high flow area though i would wait a couple hours.