Using rainwater-any cons?

Is it safe to use the water I've collected in a rain barrel that comes off the roof? My rain barrel is new so no problem there but wondered about the possibility of toxins from the roof shingles tainting the water?
The roof is over 5 years old so would think any chemicals from them would be gone by now....
The rainwater p/H is 6.8 while my tap is around 7.8.
Would like to maybe switch my tanks to half rainwater & half tap water to lower the p/H a bit.

 

There may also be a negative to this because the water from the roof could pick up all kinds of things like bird poo Etc and increase the Nitrates

 

Unless you are 100% of the pollutants in your area, I wouldn't try it. Or I'd treat the water first. These days you don't know what could be in the rain water.

 

There's also a possibility of 'acid' rain if you live in a high pollution area, it's a shame we have to think of things like that as rain should be pure, but better safe than sorry.

 

https://www.fishlore.com/aquariumfishforum/threads/using-rain-water-for-water-changes.127417/



Links of interest above.

Ken

 

Rainwater could have all sorts of pollutants. Also, I watched a documentary saying that when lightning strikes, it "knocks" the electrons off of the nitrogen atoms in the atmosphere, allowing it to combine with hydrogen and oxygen, and creates nitrates. Therefore in theory, rainwater from a thunderstorm still will have some amounts of nitrates, according to an episode of NOVA.

 

I've wondered this too as I have several friends who are all about rain barrels. I would say test it for all metrics before moving forward. Maybe try to do it on a regular cycle as levels of pollutants could change with the seasons, etc. Not sure where you live but maybe they sway based on how many people are driving, if the plant downtown is running, etc. Makes it less of a fluke and more of a pattern.

 

I wouldn't its almost impossible to say what's in there, what kind of algae is blooming or what kind of insect larvae is floating around in there. Around here in Minnesota a lot of farmers spray for crops with air planes and helicopters which could contaminate the water. Car exhaust, airborne factory chemicals, even the barrel you keep your rainwater in could seep harmful chemicals into your rain water.

I would just use dechlorinated tap water, and if you cannot use your tap water. I would use R/O water that has base Minerals put back into it.

 

Thanks everybody for your comments. I was thinking about the possible contamination from the things you all have mentioned, too. I guess I'll use the rainwater for my plants for now.