Benefit of using rain water?

Hi Prof

What are your thoughts on using rain water as opposed to tap water for aquariums?

From my experience the fish seem to love it and go into a breeding frenzy whenever I do a WC. I suppose in an industrialized urban area the gutter run-off water can have a lot of pollutants and have an undesirable pH? Also will rainwater not have better levels of micro nutrients in it as apposed to tap water?

Thanks

 

Hi ak47,

Hope you aren't going to shoot me.......

Rainwater is the same as distilled water, unless it comes off a roof that is contaminated or has galvanised iron sheeting. Basically this means that this water does not contain any dissolved substances and we therefore say that the water is very soft. It is fine to mix harder tap water with this water to then make the mix softer, but it is not good to keep fishes entirely in rainwater as it does not contain any salts. As a result, the kidneys of the fishes would work very hard in such water.

If you are trying to breed softwater fishes then it is good to mix rainwater into your tapwater, but even for discus, it is not good to keep them in rainwater only. Such water is also subject the very rapid changes in pH. If you live in a polluted area rainwater will contain pollutants which is not good. I would not recommend the collection of rainwater in the whole of Gauteng and in the Vaal triangle for this reason. If you are near the refinery in Durban this may also be a problem for you specifically. Rainwater has no micronutrients and tapwater is better, but also not adequate for plant growth for example.

So, to sum up: rainwater is good when you mix it with tapwater. Rainwater is not stable with regard to pH and you have be very careful when you use such water. Rainwater does not contain any micronutrients.

Hope this answers your questions.

Kind regards,

Dirk

 

Hi Prof

Thanks very much for the insight!
I have been using rainwater to skip the de-chlorination step of tap water. Come to think of it, i have been using tap water to top-up my tank from time to time which probably helped keep my fish kidney's intact. Would the addition of table salt or KCl not help the cause?
I live in the rural part of Kzn so perhaps acid rain/pollutants is not really an issue in this part of the country?
Also would there be benefits of using borehole water? I know borehole water can vary in chemistry depending on location? Would this have a high level of micro-nutrients?

 

Hi ak,

I would not recommend the use of salt or KCl as these are not natural salts that occur in river water systems. I would recommend my DSD plant hardening mix as this contains a balanced mixture of Calcium and Magnesium.

Rural areas in KZN are not a problem regarding pollutants in rainwater so that is fine.

As you say, borehole water can vary drastically depending on location so unless you have an analysis done, you would also not know which micronutrients may be present, and over time this may vary as well as ground water is also fed by rainwater or in drought periods the ground water becomes harder. If you want a balanced plant micronutrient mix, I would recommend using my DSD plant feeding mix.

Kind regards,

Dirk