Becca
Members
I've always been concerned about contaminants in rainwater (e.g. chemicals from shingles or elsewhere). No issues?
Not so far. I keep a 30 gallon trash can in the house that I drain the barrels into, as needed, so I can heat water and add a bit of Prime (just in case there are any metals in there). Occasionally one of my bug screens gets a hole and I accidentally end up raising mosquitoes indoors (oops), but that could happen with standing RO water, too.
Water comes off the roof at about 20-25 ppm tds. I've bred chocolate gouramis, L183s, and Dicrossus in it. I've even had B. cupido spawn in it (though eggs were eaten quickly).
If you've got a particularly old house (prior to 1975), it might be worth testing with some cheap dither fish, but I haven't had any problems.