Distilled Water to Lower pH/kH

Distilled Water to Lower pH/kH (Update)

Hi. I thought I'd post an update covering the results of my distilled water experiment.

About 10 days ago, when I started this thread, I did a partial water change, adding about 8 gallons of distilled water from the supermarket to my 40 gallon tank. I monitored the water over the week, and on Sunday (two days ago) I did my standard tank servicing, changing out filter media, vacuuming and doing a 25 percent change, with tap water.

I just re-tested the water, and it's about the same it's been all 10 days. pH is now about 7.2 (down from the very off-scale high it was - I guessed around 9.0). KH remains high; about 268.5 ppm, but that's down from 358+ before I added distilled.

All the fish are very active and seem happy; they are feeding well and behaving normally. I've added a few new fish (guppies and corys) and they have had no problems.

The only side effect is that the water is just a touch cloudy, a very slight milky hue. I'm not sure what is causing it but I'm monitoring it. All other chemistry seems good.

So for now, I'm calling this a success. I'd still like to see the KH a little lower, but the pH is good and appears to be stable (though of course it's too soon to be sure). I'll be happier when the water is totally clear, of course, but all in all I'm pleased with the results.

Thank you all for the advice!
 
I hate to chime in this late in the life of this thread, but I spent the time to read the whole thing and I see some things that seem out of synch.

Firstly, all the posts about the tank chemistry are dealing with pH and KH. There is no mention of TDS or GH which are often more of an issue than pH.

Secondly, the math doesnt "add up":

About 10 days ago, when I started this thread, I did a partial water change, adding about 8 gallons of distilled water from the supermarket to my 40 gallon tank. I monitored the water over the week, and on Sunday (two days ago) I did my standard tank servicing, changing out filter media, vacuuming and doing a 25 percent change, with tap water.

I just re-tested the water, and it's about the same it's been all 10 days. pH is now about 7.2 (down from the very off-scale high it was - I guessed around 9.0). KH remains high; about 268.5 ppm, but that's down from 358+ before I added distilled.
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This is a 40 gal tank, assuming typical manufacturer's specs and then decor etc. in the tank, the odds are good the actual volume of water is in the 35 gl range.

With a pH estimated at 9 and KH of 358 ppm, replacing 8/35 or 23% of the water with distilled which is pH 7 and 0 GH, a straight proportional calculation results in a pH of about 8.5 and a GH of 275. But in reality, the changes don't occur proportionately, they are less in practice. There is no way given the numbers reported the results can be due to 8 gals of distilled. Even if the actual pH pre-distilled was 8, not 9, the result is about 7.77 pH. Moreover, KH acts to hold pH stable so, imo, there is no way to move the pH down from 8 or 9 to 7.2 with a kh of 15+dg (268ppm).

Buffering Capacity (KH, Alkalinity)

Buffering capacity refers to water's ability to keep the pH stable as acids or bases are added. pH and buffering capacity are intertwined with one another; although one might think that adding equal volumes of an acid and neutral water would result in a pH halfway in between, this rarely happens in practice. If the water has sufficient buffering capacity, the buffering capacity can absorb and neutralize the added acid without significantly changing the pH. Conceptually, a buffer acts somewhat like a large sponge. As more acid is added, the ``sponge'' absorbs the acid without changing the pH much. The ``sponge's'' capacity is limited however; once the buffering capacity is used up, the pH changes more rapidly as acids are added.

Buffering has both positive and negative consequences. On the plus side, the nitrogen cycle produces nitric acid (nitrate). Without buffering, your tank's pH would drop over time (a bad thing). With sufficient buffering, the pH stays stable (a good thing). On the negative side, hard tap water often almost always has a large buffering capacity. If the pH of the water is too high for your fish, the buffering capacity makes it difficult to lower the pH to a more appropriate value. Naive attempts to change the pH of water usually fail because buffering effects are ignored.
In freshwater aquariums, most of water's buffering capacity is due to carbonates and bicarbonates. Thus, the terms ``carbonate hardness'' (KH), ``alkalinity'' and ``buffering capacity'' are used interchangeably. Although technically not the same things, they are equivalent in practice in the context of fishkeeping. Note: the term ``alkalinity'' should not be confused with the term ``alkaline''. Alkalinity refers to buffering, while alkaline refers to a solution that is a base (i.e., pH > 7).
How much buffering does your tank need? Most aquarium buffering capacity test kits actually measure KH. The larger the KH, the more resistant to pH changes your water will be. A tank's KH should be high enough to prevent large pH swings in your tank over time. If your KH is below roughly 4.5 dH, you should pay special attention to your tank's pH (e.g, test weekly, until you get a feel for how stable the pH is). This is ESPECIALLY important if you neglect to do frequent partial water changes. In particular, the nitrogen cycle creates a tendency for an established tank's pH to decrease over time. The exact amount of pH change depends on the quantity and rate of nitrates produced, as well as the KH. If your pH drops more than roughly two tenths of a point over a month, you should consider increasing the KH or performing partial water changes more frequently. KH doesn't affect fish directly, so there is no need to match fish species to a particular KH. Note: it is not a good idea to use distilled water in your tank. By definition, distilled water has essentially no KH. That means that adding even a little bit of acid will change the pH significantly (stressing fish). Because of its instability, distilled (or any essentially pure water) is never used directly. Tap water or other salts must first be added to it in order to increase its GH and KH.
from http://fins.actwin.com/aquariafaq.html
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But then another 25% wc was done with tap and the water is reported to basically have the same params as before the tap change. This implies that the tap is about the same level as the tank. So unless the tap has been all over the map, what caused the initial numbers being so high above the tap? I do not lean to the bad Amquel explaination but can not say 100% it wasn't.

As to what could have killed the fish. One of the problems relating to tanks which dont get sufficient water changes is the build up of TDS (Total Disolved Solids) these are closely tied to what most aquariasts measure as hardness of GH. TDS can effect the ability of some fish to osmoregulate (big word Google it for more info) which has to do with a fish equalizing internal and external prssures in the water. If you do a decent sized water change in a tank where the TDS have been allowed to build up, the resultant drop can kill fish. It can do so much easier than a pH change can.

Next, there is no way doing the changes you listed after adding the baking soda that it could still be having the effect you describe on the parms.

Finally, I don't think anywhere in this thread I saw any params for ther tap water mentioned.

I am not so sure you have actually fugured out whats is up nor if it even makes sense to be messing with distilled water given the cost is $1/gal.- give or take. About 2 months of water changes pay for an RO unit if you really need the help.
 
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That's a lot more science than I know, to be honest. I really appreciate your digging into it. That said, though, the numbers I'm giving you are accurate -- or at least they're what I'm getting from my test kits, albeit with some guesstimating on my part.

I'm posting here not to prove anything, just so that others -- who helped me -- can take what the can away from my experience, for whatever it's worth.

Recapping:

Before the crash, water generally tested in the pH 7.0 range. I was not tracking KH at that time. I can't prove it was bad AmQuel that wiped the tank, and certainly think it could have been old tank syndrome. But the tank symptoms didn't match what I've read about old tank syndrome, and DID match what people on this board and elsewhere have described resulting from bad additives: murky water, very acid pH, strong smell like AmQuel, etc.

After the crash, I added baking soda to try and save fish. The tank quickly stabilized, and I have had no crashes since changing additive chemicals. But pH tested well off chart. My test kit tops out at 7.6. Based on how much darker the test was than that top reading, I guessed 9. I don't actually know. I do know the KH was about 358 ppm and had held steady for quite some time.

When I concluded the KH and pH were not going to lower through normal water changes with my tap water (which is somewhat hard, in the 7.6 range and 125 ppm KH), I decided to experiment with distilled water. I added 8 gallons to my 40 gallon tank. The following week I did standard tank cleaning and changed in some tap.

The results are a pH of 7.2 and a KH of 268 ppm.

So -- I don't know if I figured out what happened and may never know. I'm going to be a little better about testing and changing out water. But I do think that, for me, changing in some distilled was a good means of lowering pH and KH.

Your mileage may vary :)
 
Since you were using a low range ph test kit, I suspect the ph was probably closer to 8 than 9. Once they go off the scale these tests are useless.
It sounds like diluting with the distilled did the trick. Your water is still at at least moderately hard since the gh has to be at least as high as the kh.
 
Your pH and kh is similar to mine. I'll make this short (I haven't read the whole thread) . My kh is 140, if I want a kh of 70 (wild Discus soft) I would mix RO water & tap water 50/50. So depending on how 'soft' you want to go you may have to consistantly mix 50% of RO water in with every water change. I say 'RO' because I've not really heard of anyone using distilled, although I assume they're similar.
 
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