Uptake Rate and RI

For some reason, it seems like my plants do not uptake very much NO3 on a daily basis. The EI dosage I use is below. After a WC and reset, I test the NO3 (Salifert NO3 Kit) at 25 ppm and it only reduces by 1-2 ppm daily. My question is; should I dose fewer times per week? I'm concerned that if I dose as below 4X per week, I'll end up with NO3 at 100+ ppm by week's end. I think I understood Tom to say the approach is to to use for slow uptake is to dose the recommended dosage, just less frequently to address slow uptake.

Thanks for the help!

KNO3 = 1.25 tsp 4x per week
KH2PO4 = .25 4x per week
MGSO4 = .25 1X per week at water change

Flourish = per instructions
Flourish Iron = per instruction
Flourish Excel= per instruction


Tank: 150 gal. dosed as 130 gallons of water
Light: 4X 96 watt PC (2.56 wpg)
Photo Period: 14 hr at 2 X 96 watts and 5 hrs at 4 X 96 watts
KH = 16
Ph = 7.3
CO2 = 24 ppm

 

Re: Uptake Rate and RI

Thanks Tom,

Is it possible my slow uptake and slow growth could be from some other limiting factor like potassium or iron? Also, have you ever heard of high KH or sodium levels slowing down growth?

I raise my KH with aking soda and I also add African rift lake salts at WC.

Thanks!