GH = 0, kH=240, What does this mean?

AlainaToadpipe

I finally got my water tested by my lfs and the gh came up as 0, but the kh came up super high. The girl suggested this might be due to having just changed the carbon filter (I did forget to let it soak, though I did rinse it). Are there any other things that could cause the kh to be high like this? I did not get the tap water tested, just the aquarium water.

10g, planted with filter, new filter cartridge last weekend, one betta as occupant for the last 24 hours, temp 73F avg. , no medication or anything added except stresszyme when tank was first set up. PH of 8 at last check. Substrate is pea gravel and aquarium "natural" rocks.

Byron

The KH or Alkalinity is from the source water. Fortunately it has no effect on fish or plants. But it does buffer pH. If memory serves me, you have well water. Obviously there is some mineral substance in the ground water that is raising the pH and KH. This is not calcium or magnesium, as they would show up in a higher GH.

This is a situation where I would want to lower the KH to get the pH down. The zero GH is fine for soft water fish, but a lower pH is also important for such fish.

While carbon in filters will adsorb DOC (dissolved organic carbon) which in turn will raise pH by removing carbonic acid, I cannot see that raising KH. So this explanation I would discount, though my chemistry is not advanced and I'm prepared to change this view with support.

Byron.

AlainaToadpipe

Okay, this is good news. The killifish profiles I've been reading are seeming to show that they prefer from 7 to 9.5ph depending on the variety. Since I'm getting a mix and won't know until they are larger I'm thinking the ph of 8 that I have for now will be a good starting point. Knowledge Base - Seriously Fish Even if I want to have a ph of that range, would you recommend I still lower the kh? It seems as though with it as high as it is, even lowering it by a substantial amount won't cause it to tip into the super soft range where maintaining ph could become more tricky.

I'm technically on city water, but since we're on an island and it's got some 100 water "companies" that are regulated by the PUD, it's really hard to know exactly how much is from what or where. I just know that all in all, it tastes really good. ;)

Byron

Ah, that may explain things. The water people are probably adding something to raise the pH. They do this here in Vancouver, I can never remember what they use, it is some form of ash, and it raises the pH from 5-ish to 7 or 7.2, but it adds no GH or KH. So in my tanks, the biological process lowers the pH within days down to 5-6, and water changes have little effect because the tank is stable and the KH being zero means the pH of the incoming water quickly evens out. I see a change of say pH 6 before to 6.4 immediately afterwards, but by next morning it is back to 6. This is harmless.

See if you can find out from the water people just what they are doing to raise the pH. I always like to know what's in my water, whether I see problems or not with it.

On the fish, if their preferred pH range is above 7 then I would not worry about yours. It would be much more significant if the range is acidic and you are providing basic (alkaline). For these fish this is not wise. But a basic pH range is probably not trouble.

AlainaToadpipe

Oh yay! I will give the PUD a call to see what all gets added, as you say, it's good to know just what's going in. That will also make any water changes a lot easier, since I won't be having to adjust the water umpteen ways before it goes in the tank.

Thank you for all of the info!

Quantum

soda ash - sodium carbonate, it should increase KH because of the carbonate anion and it can also decrease GH, at least that caused by Ca, by forming CaCO3, which then can precipitate out

AlainaToadpipe

Ahh okay, that actually makes perfect sense.

God I love fish keeping, I'd forgotten how much chem is involved. As you quote says, Byron ;O)

Byron

Yes, that's what Van adds, soda ash. But it has no effect on KH. You might find this chart interesting; I keep saying our water is near zero GH and KH, this proves it. Both GH and KH are less than 1 dGH/KH at their highest average.
http://www.metrovancouver.org/about/...emPhysical.pdf

The three water reservoirs fill with rain and snow melt, which of course is quite acidic and very soft. And the reservoirs are in the North Shore Mountains of the Coastal Range of the Rockies, and the rock is granite which is lacking in most all minerals so the water does not come into contact with mineralization. Vancouver Island is the same, as is the Pacific Northwest. East of the Cascades I believe it is different.

AlainaToadpipe

That really is an interesting chart. Luckily the fish I want to raise seem like they'll do best with the tank as is, but as I branch out and get my own tank (the one that isn't shared with my sons), I'm more and more tempted to go the rainwater rout. We tend to have nice, clean air here, comparably, so I'm not as worried about it as I would be if I was in, say, the LA area. But at the same time, I half wonder if it isn't trading one set of issues for another.

Quantum

Yes, all three water systems have low GH and KH untreated water. But I think the data supports my statement regarding the soda ash. The Capilano system does not adjust for pH or hardness and those parameters are little changed from untreated to treated. The Seymour system uses CaO (lime or quicklime) to increase pH and alkalinity, and the numbers reflect this: from 3.3 untreated to 8.4 treated for alkalinity and 6.4 to 7.1 for pH. The lime also increases Ca (1.62 to 3.27), which in turn, increases hardness from 4.64 to 8.77. The Coquitlam system is the one that uses the soda ash. Notice the big increase in alkalinity in the treated water (from 1.7 to 11.4), pH increases from 6.3 to 7.3. The amount of Ca and Mg (and therefore GH) is not affected.