Last night I thought about how to change the water parameters in the running 120-liter tank ………… and I think, maybe you are right, Helene, and it’s too difficult to change the parameters in such a lot of water in a running system.
The actual water parameters are pH 6,5 – KH <4 - GH <8 - it would not be the greatest problem to decrease these, because it's rain water mixed with tap water. Our rain water has no measurable KH and GH, a TDS of around 30 µS and pH 6,0 - if I take pure rain water, I can easily lower the pH to 5 or 5,5.
But the TDS in the tank now is around 250 µS ....... I think due to the soil, the rocks and organic material like hazel twigs etc. in the tank. I'm afraid - to lower the TDS would mean to empty the tank. And that's something I do not like to think about .........
Does somebody else here have experience in changing the water parameters of a running system?