Tds Accumulation With Ei

Hey all,

I recently bought a TDS meter and measured my tap water at 80 TDS. Just before a water change a week ago my TDS was at 260 ppm. I changed 50% of water, and as you'd expect TDS was around 170ppm. A week later, I did another 50% water change but now TDS is at 200, so it is steadily rising. During the week I add the ferts daily with an autodoser and feed the fish once a day, making sure no leftovers remain in the tank.

After a recent 50% water change NO3 was measured at 25-30 mg/l , PO4 maxed out the scale at >1.8 mg/l and K maxed out the scale at >15 mg/l. I am dosing a total of ~21mg/l worth of NO3, 3.8 mg/l PO4 and 15.7 mg/l K and 0.85 mg/l Mg weekly.

I don't know how many ferts I should expect to find in the water, but that doesn't bother me considering it's EI. What does bother me is that if the rate of TDS increase remains stable and I keep doing only one 50% WC per week, my TDS would be at 1800 in a year. That doesn't sound healthy, and this leads me to believe I may be adding too many ferts and that my plants are consuming no where near of what I'm adding. Everywhere it is said that we do large weekly water changes to fight the excess ferts, so I would expect this means resetting the TDS as well.

 

Update: I effectively zeroed my tank with a 50 + 30 % WC. Now everything went to tap water levels, except K which was 15 ppm after the 50 + 30% wc. This means it was around 40 ppm before. Also tested tap and got 0 ppm K as a result. I have been dosing around 15 ppm worth of K per week while doing 50% wc weekly. I've been doing this consistently for the past 10 weeks. Why is only K building up, and so fast too?