TDS is all I need to know? Seems to work for me...


New Member
Jul 16, 2017
Hi there,

I have moved 6 months ago from EI to PPS only because I was tired of big weekly water changes. My tank is 120 Liters, with medium/high plants load, with medium fish load, medium/high (PAR around 70 st the bottom) with adasoil (about 2 years old), RO water, KH2, Ph 6.2 ( 1.1 unit down when co2 is on) with dwarf baby tears carpet, AR mini and a few easier plants. Plants are all doing fine with no noticeable algae on plants or ricks
( I clean the glass weekly to remove an almist unnoticeable layer of algae that starts growing only on glasses). I have only dragon rock and lava rock, which I have soaked for days in ro water with unchanged TDS readings before using it in the aquarium. So, I assume I have no significant mineral leaches into my aquarium water that may affect the TDS readings.

I dose very, very lean counting litterally drops of some sulutions I mostly made. I dose every day the following (with double of the doses below plus 20 ppm. Ca, 10 ppm Mg and 10 ppm K after 50% water changes that I do once x month):
NO3 0.5 ppm
PO4 0.05 ppm
K 1 ppm
Profito Easylife 10 drops (this is 0.3 ml)
Fe DTPA 0.03 ppm 10 drops
Flourish trace 10 drops

The TDS reading after 50% water change and the addition of Ca, Mg and K is around 110 ppm.

The point is that the TDS reading does not change over weeks. It stays consistently there one or 2 ppm up or down.

I trim the plants in order to have always a similar plant mass. So they should consume the same nutrients over time.

Can I dare to draw the following conclusions:
- I have found a stable sweet-spot/ balance
- I may remain in the sweet-spot/ balance also if I further reduce water changes, just making sure to slightly increase or reduce over time my fertilization in order to keep the same TDS reading?




Super Moderator
Staff member
Lifetime Member
Jun 20, 2016
TDS, actually the device measures water Electrical Conductivity (EC) , is a sum parameter hence cannot say anything about the individual concentrations of ions in mixed solutions.
The water can have the same EC while K keeps accumulating and Mg keeps running lower and lower for example. Likely a lot of stuff are running very low thus starving the plants for the nutrients they need to growth.

EC is a bad at telling the concentration of organic substances.

sure i guess you can say you arrived in a sweet spot of having a TDS of 110. It's very similar with people doing everything they can to keep the pH at 7.00 or ORP at 357 mV . If that works for your setup then relax and enjoy.