Correct yes.Test is easy.
You shouldn’t be a trend for your tank and the phos in it. Just watch that trend with food now being “clean”.
You can also see if 1ml of strained food to 10 ml (or whatever) of new sw will show high levels of phos when tested.
Just remember, phos is still being added with food, just not near as much.
This isn't a magic bullet, but if I can effectively remove 25%?? Of phos going in on the daily, I hope to be able to get it under control and within range.
Currently, I'm burning through gfo faster than my 500 ppm source water kills my DI resin.
This will hopefully be one step of a multi tier approach for long term stability.
As for the test. I think I will do a straining with all seven types of foods that I use in a given amount of water, keeping back the waste water. Stirring that at nauseum then adding it to 1 cup of pre tested fresh SW.
The total rise should give me the average phos saved from each cube. If the rise is too high, I can then dilute the sample 50% and try again.
And of you science nerds have any adds?