Rotala butterfly question
I'm wondering if someone could chime in and explain how this works. Trying to understand the ' science' of a planted tank a little better. I have a 20G long that I dose 1/8 tsp. of KNO3 3 x a week..... I use E.I., but I'll just use KNO3 as the example. When I type in 1/8 tesp of KNO3 and hit 'result of my dose ' I get 6.89ppm of NO3 ( no real need to give the N and K ) I do this three times a week. If I hit 3/8 tsp. ( total dose for the week ), obviously it jumps to 20.66. So my question is, I like to keep logs of what I do, so does my tank have 6.89 ppm or 20.66 ? I figure it gets used up on the ' off' days. I hear people mention they run XXppm of such and such, and I'm just trying to figure out how they arrive at that number. I hope this isn't a stupid question, just a little confused .
Thanks in advance for any help .