I am a newbie and I'm about to set up two new tanks very soon, one a 70 gallon and the other a 29 gallon. I already set up a ten gallon tank last week with Eco Complete and RO water, some hornwort, and two mollies. (no CO2) I have water softened water in the house, unsoftened water at the outside hose connection, and RO water I get from the softened, inside water. My water softener was bought to get rid of a sulfur like smell and at the same time we also installed a rust master water filter to get rid of the iron deposits in our toilets and dishwasher, etc. All of this water is from an artesian well. The PH of my water has always been high and in past years when I had fish tanks it always interfered with my growing plants and no matter how much "PH Down" I used I couldn't get the PH down much and only managed to kill some fish. This was before I was aware of CO2, better lighting, and substrates.
Here are my water readings: Softened tap water:PH 8.2 GH 4 KH 4 RO water: PH 6.4 GH 3 KH 3 Outside hose water: PH 8.2 GH 6 KH 5 Fish tank water: PH 7.8 GH 5 KH 4 (phosphate 1 in tap and hose and 0 in RO)
I am surprised how soft my water is and yet the PH is high. I am also surprised how much KH and GH gets through the RO unit, maybe the motor is pushing it through too fast, it does give 4 gallons an hour. (It is a 100 gallon per day unit so that may not be the cause. I only get a gph with the motor off) I took many test readings to verify these findings.
My question is what water should I use to make water changes? I will be setting up the tanks with Eco Complete and RO water and using CO2. I know that the CO2 will bring the PH down, but what water should I use thereafter? Should I mix 20% Tap (or more) with RO? (after 24 hours this read PH 7.6) I could see a problem with using 8.2 PH tap water in a tank that due to CO2 has a 6.8 PH. Any thoughts?