distilled water seems acidic

[iheartbettas]

I'm going to gradually lower the ph in one of my tanks that houses a few apistos by mixing distilled water with my tap water for my next water change. I bought a gallon of distilled water and tested it with my API test kit. It turned out to be (according to the color chart), around 6.4! I've read that distilled water is neutral at 7.0.

I know for certain it was not the green color which is for 7.0. Is it normal for distilled water to be this acidic or is my API master test kit defective? It's not even 6 months old.

Thanks for your thoughts.

 

[SubRosa]

Theoretically pure distilled water has a pH of 7. But in reality since it has no buffering capacity any small impurity can change the pH considerably. A slight imbvalance between O2 and CO2 is the most likely culprit. It's nothing to worry about.

 

[prober]

I have used distilled water and RO/DI water quite a bit and there are some things you need to know before using it.

First, it is just water. No minerals, trace elements or even oxygen usually. Therefore you should take some precautions when using it. There also is usually no heavy metals, chlorine, nitrates or other polutants. This can be very good since you know what is in it and can add whatever you need to make it acceptable for your fish.

The first thing I do with mine is to add some buffers since there is no buffering, or carbonate hardness. In my case I add Seachems alkaline buffer and acid buffer. There is a ratio formula on the bottles and I add that in until I reach my desired hardness and ph. This ensures that the PH, KH and GH of the water is correct. Without doing this the PH of the water can swing drastically. If you are cutting your tap water with this then you would need to experiment with amounts to know whether to mix it 50/50 or less to get the desired hardness.

The next thing I do is to aerate the water for at least an hour. Distilled or RO water will be very oxygen depleted and the first time I used it I found that my fish were all gasping at the surface. Since aerating the water beforehand I have not seen this behavior again.

The final thing I do is to add some seachem "fresh trace" which has some electrolites and other trace elements that not only are missing from RO/DI water but also get used by the animals and plants in the tank. Sort of like Gatorade for your fish.

If you are mixing this with tap water you may not need to add the traces and you may not need to add buffers if your tap water is very high in carbonate hardness and the PH will probably revert to something very close to your tap water since that is the PH that it is buffered at. You will need to get a GH/KH test kit if you don't have one so you know what changes you need to make to have this water be safe for your fish.

Aerating is still needed unless you want to sufficate your fish.

Hope this helps.

 

[rstrobel]

I'm going to gradually lower the ph in one of my tanks that houses a few apistos by mixing distilled water with my tap water for my next water change. I bought a gallon of distilled water and tested it with my API test kit. It turned out to be (according to the color chart), around 6.4! I've read that distilled water is neutral at 7.0.

I know for certain it was not the green color which is for 7.0. Is it normal for distilled water to be this acidic or is my API master test kit defective? It's not even 6 months old.

Thanks for your thoughts.

the distilled water that I've tested before was around 6.4 as well.

 

[prober]

I agree it is slightly acid and has almost 0 hardness. By itself it is not liveable for fish or plants, or people for that matter.

That can make it quite usefull for lowering hardness but since it has no buffers I am afraid that the PH of your water will slowly go right back to where it was since that is what it is buffered at. And if there is not enough buffering capacity,(carbonate hardness), then you could experience large PH swings. The proper way to lower the PH would be to use acid and alkaline buffers. By using them together you can raise or lower your PH and it will remain at whatever PH you have adjusted it to, without lowering the GH and KH.

Whatever you do, do not use the bottles of "PH up" or "PH down". Those contain no buffers and will only give temporary results sending your PH on a rollercoaster ride that will not be good for your fish.

Think of PH as the speed of your car and buffers as cruise control. You can adjust your speed but without the cruise control it will eventually wander faster or slower. You use the buffers to raise or lower your PH and once set it will stay there. Your tap water already contains buffers so simply adjusting the PH without adding the right buffer will not work. The PH will just go back to where it is buffered to. In the case of distilled water which has no buffers the PH can be affected by even the smallest environmental change.

What is the GH and KH of your water from the tap?

 

[Mgamer20o0]

Theoretically pure distilled water has a pH of 7. But in reality since it has no buffering capacity any small impurity can change the pH considerably. A slight imbvalance between O2 and CO2 is the most likely culprit. It's nothing to worry about.

most likely subrosa is 100% correct on this.

how come you are adding distilled water?

 

[sorberj]

I guess my question is why do you want to lower the pH in the aquarium? How far off is it now?
If you're wanting to lower the pH for apistos, unless your pH is wildly off, you may be better off going a little bit less of a manual route. Putting peat in your filter media will drop the pH and add a lot of other compounds to the water that the apistos will likely recognize. Additionally, you can also add driftwood (which will also soften the water). These two things are the most common methods for dropping pH and/or hardness for keepers of South American (particularly Amazonian and Orinocan) species like Apistos.
I generally view the use of direct chemistry manipuation to be a less than ideal method because your water chemistry becomes dependent on you taking specific actions during each water change. With that said, if you do need to go this route, I think the previous posters have already given some solid advice.