Using Rainwater?

[BarrierReef]

Hi. My tap water ph is very high. Around 7.7
Ive had some problems with it affecting the health of my fish
Glowlight tetras, Melon Barbs,Five banded barbs,female Bettas, Rummy nose tetras amongst others......
I was considering collecting and using rain water slowly over a period of months in slow amounts added during water changes to slowly get the Ph down to around 7.0. In theory the tank would then eventually only use rain water with a neutral ph?
I was wondering about what others on here think to the idea? Safe or not? Ive often seen people taking large containers down to the garden centre to buy RO water but wanted to avoid that cost and hassle if i could.

 

[fluttermoth]

Rainwater is fine to use, as long as you live in rural area, with no industry within 15 or 20 miles. Using straight rainwater is not a good idea; it's so soft that the pH can 'crash' where it drops very rapidly; sometimes to pH 5 or even lower; you'd need to add some tap water or remineralising liquid to stop that happening.

A pH of 7.7 is not that high and your fish should be doing fine in that; I suspect your problems are being caused by something else.

Have you tested your water? Is your filter cycled?

 

[Joshwainwright]

You can add rainwater but your pH should be fine, your fish will be able to adapt to it. For the problems, have you checked for ammonia spikes?

 

[TwoTankAmin]

Please do a bit of Googling about the pH of rainwater. Understand why it is normally in the mid 5s and the relationship of CO2, carbonic acid etc. Incidentally, a lot of the chemistry it discusses can also be seen at work a tank. This is a decent link but does have a bunch a formulas. Reading the text though will give you some idea of what is involved in rain water.

http/www.chemistry.wustl.edu/~edudev/LabTutorials/Water/FreshWater/acidrain.html

It is a link about Acid rain. Before they get to the acid rain parts they explain about more "normal" rain quite decently Acid rain is even lower pH and is mostly caused by man made pollution. Depending on where one measures rainfall, its acidity will be effected by that areas atmospheric contents. The upshot is that rainfall with a pH as low as 2.0 has been measured in some places.

If you want to use rainwater in your tank I suggest you make sure you are aware of the chemical makeup of the rain in your area as well as your tap water. This information will give you an idea of what you are trying to control/change and what mixing them might yield. There is no reason in, most cases, not to use rainwater as long as you have a handle on things.

Many folks who work with altering water parameters in tanks prefer to work with RO or RO/DI water as it gives one greater control and accuracy. But then you do have to spend for the unit to make it while rain is free.

Collecting rain water in any quantity is usually going to involve collecting in from "run off" sources. That is as it comes off a roof and down the downspout of the roof gutter system etc. Even if you have big rains and a huge container to try and catch it in, it will be exposed to what ever is blowing around at ground level. Rolling off the roof and down the spouts it may also pick up stuff. So never simply assume you are getting safe water collected, be sure of your collection methods.

Finally, if you are talking about a small tank here and the need to lower the pH ony a few .1s, then you may be able to do it with minimal amounts of distilled water from a supermarket or ro water from an lfs/lps.

 

[CezzaXV]

I'd also like to point out that rainwater won't necessarily have a pH Of 7 as it may have pollutants in it, and you won't be wanting to put that into your water. It will also land you with difficulties if you run out of rainwater - you'd need to be collecting quite a bit even for a small tank.

Another more reliable option would be reverse osmosis water, but tbh 7.7 isn't extreme and there are many fish that would be perfectly happy in it. I have soft water that occasionally drops as low as 6.0 (further from neutral than yours is) and its not caused me any trouble.

 

[Aqua Tom]

A pH of 7.7 is fine. It is unlikely to be that that is effecting your fish.

My pH is 7.8ish a my fish cope very well.


Tom.

 

[OldMan47]

I collect and use rain water in my tanks. I always wait until it has been raining a while to get rid of most of the dust that builds up on surfaces between rainfalls before I collect any. You use rain the same way you use RO. It has almost no mineral content and is just too soft for anything most of us keep. Instead you end up mixing it with tap water to get the desired water mineral content. I would use that mix for each water change and after a few changes you should see your tank water approach the same mineral concentration as your blend. In my case my tap water is around 225 ppm of TDS, total dissolved solids. I mix it 2 parts RO or rain to 1 part tap water to make water for things like cories or angels. I do not worry about pH because I know it can easily vary 1/2 point on a daily basis in natural environments. Rapid pH change is not harmful, within reason, but rapid mineral content change can cause extreme distress of more sensitive fish. It is why I suggested you only add your blend during water changes rather than raw rain water alone.