Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
GH and KH of the rain water are so close to zero that the test is not showing any. pH was pretty close to neutral. TDS really low, but not zero. Usually single digits. Nitrogen (Ammonia, nitrite, nitrate) zero.
I do not add minerals since I am using the rain water more like a top off, with just a little bit of water removal. Gradually, over the course of the winter the GH and KH are coming down.
This is what I want.
When I did larger water changes I would do this:
A) Rain water into a barrel in the house. (Actually I have 3 barrels totaling about 100 gallons)
B) Add a knee-hi stocking of peat moss, circulate it overnight. The heat from the pump would help, and the water would be room temperature the next morning, and would have the organic acids certain fish wanted. (not all the barrels got this- only a few tanks were black water tanks)
C) Add hot water from the tap. This would:
1) Raise GH and KH to where I wanted it (Tap water is very good, but some fish prefer it even softer, so the blend of tap and rain was just right)
2) Warm the water even more. Since I was doing larger water changes I did not want that much difference in temperature.
D) Add dechlor, plant fertilizer as needed. Circulate until whatever I added was dissolved, thoroughly blended with the water. Few minutes, or just long enough to vacuum the tank.
E) Do the water change promptly, while the water was still warm.
I do not waste rain water on hard water tanks. I have pretty good tap water, and have to add minerals for my Lake Tang. tanks, so why bother starting with rain water?
I use rain water only for tanks that want to have softer water. Then blend with tap water if I am doing a large enough water change that the TDS would drop too much with pure rain water.
If I had more problems with the tap water, then I would look into better rain water storage, and use it without adding tap water, but would need to add minerals.