Demineralized water help please?

[Mariachi]

Hi all.

I am thinking of adding some demeralized water into my partial water
changes to try and bring the hardness down. I would probably be adding
1/4 demineralized and 3/4 regular water back into my tank.

I was just wondering how/if this affects the PH and anything else I
should watch out for?

[dc]

"Mariachi" > wrote in news:1159570104.069224.245590
@b28g2000cwb.googlegroups.com:

> I am thinking of adding some demeralized water into my partial water
> changes to try and bring the hardness down. I would probably be adding
> 1/4 demineralized and 3/4 regular water back into my tank.
>
> I was just wondering how/if this affects the PH and anything else I
> should watch out for?

It depends on the condition of your normal water source and the pH of the
demineralized water you plan on using. Unless it is true RO water it is
unlikely to be completely devoid of solutes, but it probably fairly low in
them. Pure water will have a pH of 7.0, but your demineralized source may
be quite different.

That said, the amount you are adding in to your water changes is rather
small, so the only noticeable effect is probably going to be a slow
lowering of your carbonate hardness (KH) which will have a gradual negative
effect on your aquarium's pH over time.

A high KH will cause a high pH, so lowering your KH will also lower your
pH.

[carlrs]

Mariachi wrote:
> Hi all.
>
> I am thinking of adding some demeralized water into my partial water
> changes to try and bring the hardness down. I would probably be adding
> 1/4 demineralized and 3/4 regular water back into my tank.
>
> I was just wondering how/if this affects the PH and anything else I
> should watch out for?

I have used RO water in different proportions with tap-water for my
Discus aquariums for quite a while with positive results. The
proportions you use will vary (as dc mentioned) according to the
condition of your tap water. I generally added about 50/50 RO to our
7.6 pH tap water and also use a lot of peat in the filters, this way I
was able to add some calcium to the water without affecting the pH to
adversly (discus do better with some calcium available).

Carl