I got a 0 ppm result. Do I need to do this test again today?
Yes, I would redo the test again.
Why? The OP messed up by adding one more drop by accident. I'd try again just in case because directions say 8 drops and the OP did 9. Maybe the results would still show 0, I don't know.
As long as there is enough of the reagent present for the reaction to occur, it'll occur. If the OP got something like 1ppm, I'd retest. With a 0 reading another test is just wasteful.
I'd still do it again. But that's just me.
I think I'll do another tomorrow. I couldn't do it earlier because I had to go take care of the office fish, then I had to do some grocery shopping. I'm exhausted now lol.
Pretty sure another ammonia test would take under one minute. Much less strenuous then launching this thread, monitoring responses for a day and replying to them.