How soon to test CYA after granules in sock are out?

[Ticojpunk]

I put a pound of CYA in a sock hung in front of the return jet today for a few hours and it’s all dissolved. How soon can I check my CYA level and expect an accurate result?

 

[mknauss]

Next day with pump running.

 

[wireform]

As @mknauss ^^^^^^ but for treating purposes consider it done.