Using Rain Water

philak · Nov 1, 2009

As mentioned elsewhere i have very hard tap water(KH 11, GH19) which i would like to soften using rain water if possible. I intend to transfer some neon tetras to this tank form my g/fs so i really do want to soften the water. To that end i've bought a rainwater butt today and have started collecting. Being England it shouldn't take long!

I've seen plenty of threads where people use 50 % rain and tap water which should have the added benefit of lowering my PH slightly as well as softening my water. A few threads mention possible pollutants in rain water but never mention any specifics. Is there anything in particular to look out for and does anyone else here use rw. If so do you pre-filter it (like through a mesh or something?).

The tank is also planted and i understand that softer water will help there too.

Cheers

OldMan47 · Nov 1, 2009

A lot depends on the roofing material that the water is running across. In my case I personally put a new roof surface onto my roof about 3 years ago and know that what I have up there is not a threat to my fish. I wait until the gutters have been flushed well by a new rainfall and then start collecting rain water to use. The flush gets rid of the dust and such that builds quite quickly between rains, because I live in an agricultural area where plowing and harvesting activities can stir up a fair amount of dust. I find that I can measure my rain water at about 8 ppm of total dissolved solids where even my RO, not an RO/DI, only gets me down to about 20 ppm of TDS. I would expect a proper RO/DI to get water down even lower in TDS, to around 3 ppm or less, but when I intend to mix it back in with tap water I really don't see the point to doing that. By living outside the highly industrialized areas, I do not worry too much about what trace chemicals might be entrained in the rain water. I might do things differently in if I lived elsewhere. Where I am I just use the water as if I knew for certain that it was pure. I am confident enough in my technique that I would not hesitate to drink it really.

philak · Nov 1, 2009

Thanks Oldman.

To the best of my knowledge there is no heavy industry pumping out toxins anywhere near to me. My roof is twenty years old and made of tile so presumably not old enough to be breaking down but not new enough to be leaching anything bad although i'm not sure of the composition. I will of course be testing the rain water for all the usual things that API supply kits for.

I also had very heavy rain last night so starting collection today should avoid any dust as you mention that might have been lying around.

As a bonus , if it works it will reduce my metered water bill

BigC · Nov 1, 2009

I have made a tray, (Plastic lunch box)with holes drilled in its base is sits just inside the neck of the rainwater butt and I can fill it with either peat or activated carbon to filter the rainwater.
I also utilise RO in conjunction with the rainwater. The RO comes out at 1ppm TDS. I use 10ltr buckets and a ltr measuring jug.
You will have to mess about with different permutations of course to get where your personal needs lay.
8ltrs of rainwater to 2 ltrs of RO come out for me at. pH 6.4 and I then lift the TDS to 36ppm which is 2'dKH.(17.9TDS = 1'dKH) to help stop a pH crash.
This is ideal for me breeding soft-water killifish. If you add peat or similar blackwater extract then you will push up the TDS.
If your just into keeping fish rather than breeding I would just filter your rainwater through activated carbon and mix with a little tap-water testing all the while.
ATB
C

philak · Nov 1, 2009

Thanks BigC.

Since Oldman mentioned TDS i've been looking up a test for them but only came up with an electronic pen type test that seemingly only measures some types of TDS ie those that affect conductivity.

Can either of you tell me how you are testing for them?

Ta.