ADA Aquasoil - effects on water chemistry?
I bought two 9 liter bags of ADA Aquasoil Amazonia for my 46g planted tank. It states that the soil lowers ph, and softens water making it suitable for most plants, and is clay based which is great for most root feeders.
Background. I've had this tank up and running for several months now, light - medium stocked with plants, heavily stocked with fish. Nitrates reach 20ppm inside a week, so I've been doing two water changes per week lately. I have also started dosing dry ferts - K2SO4, KH2PO4, and CSM+B. 1/8teaspoon of each, three times a week.
I have been testing the water parameters on this tank quite bit lately. I just started up CO2 injection and I wanted to see what my ph was sitting at. So... here we go. Ph out of tap is 8.2, after sitting for 24 hours, its 7.2. Ph in the 46g with the aquasoil is 6.4. I have been testing this since day one, and it has not changed. The ph is always at 6.4 and there has been no fluctuation.
Dig a little deeper. Kh out of tap is 4, and Gh is 9. Kh in the 46g.... undetectable, Gh in the 46g is 6. TDS of tap 177ppm, TDS in tank 193ppm.
So not sure what the deal is with the KH, but I tested several times. The first drop in the tube and the water turns yellow.
Is this even possible or is something in the substrate leeching out and throwing off this test?