dosing in the fowlr.

[Ruth]

What I do in my FOWLR is test it monthly and adjust as required (usually not very much as there is really nothing using those elements)
I like to try and keep my water as close to natural sea water as I can - to my little pea brain it just makes sense that the critters are going to be happier in as close to their natural environment as our sad attempts can duplicate.
If you are using a good balanced salt brand you should rarely if ever have to adjust.