I hadn't heard of "Prime' before. The discription at thier web site sounds pretty good.
There was one sentence that caught my eye.....
Prime® also contains a binder which renders ammonia, nitrite, and nitrate non-toxic.

I wonder if the binder prevents the plants from using the 'N' ?
( I always forget which one the plants actually use...nitrates or nitrites)

I guess it wouldn't be much of an issue, especially if one is just pre-treating make up water (?)
What do you think Badflash ?