Kh Khonfusion

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R

rye

Feeder Fish
MFK Member
Jun 13, 2008
38
0
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Tennessee
How bout that snazzy subject line? eh? eh? this thing on?

I've been reading posts on MFK for a long time now but never made a post. So hi everyone, I'm rye and I live in Tennessee. I have a question and I've used the search but cannot seem to find any information. I included as detailed an explaination as I could, but if you dont need to know that stuff, the last two paragraphs sum things up. I am setting up a new 125 and here is the situation:

Tank: 125 gal (72 x 18 x 22)
Filtration: 2 x Eheim 2217, marineland magnum 350 w/water polishing media only
Substrate: Aquariumplants.com substrate 3-4 inches deep
Lighting: 192w power compact (2 x 96w) 6700k
Decor: Malaysian driftwood, cocanut halves, slate, green pebble (trade name no doubt, not sure exactly what kind of rock this is)
Temp: 79 f (2 x 200w inline heaters on the eheim outputs)

Will be using pressurized CO2 just havent set it up yet.

Bioload: I am just setting up, at the time of the tests, all of this had been in there for approx. 24 hrs.
2 x small crypts
12 x zebra danios

The cocanut halves and driftwood were boiled until boiling for 20 min left clear water. They were also cleaned with diluted bleach and then soaked overnight in a heavy solution of water conditioner.

So here is the problem, Before I even started I tested the parameters on the tap water:

Ph: 8.0
Gh: < 1 dGh
Kh: 9~10 dKh

I filled the tank and let the filters run and heaters warm up the water for 4 days. On the 5th day I added the crypts and danios. On the 6th day these were the readings for the tank water:

Ph: 6.4
Gh: < 1 dGh
Kh: < 1 dKh
Ammonia: < .25 ppm (but more than 0)

Thinking I'd lost my mind I tested 4 more times, getting the same results. I then tested the tap water again multiple times to make sure my original tests werent bad and got:

Ph: 7.6
Gh: < 1 dGh
Kh: 7 dKh

so my tap water which at different times was reading 7 to 10 dKh went into the tank and is now less than one degree. I didnt think carbonates could just kinda go out of the water. If it were just the Ph swing I might attribute to the driftwood and cocanuts maybe still leaching a little and the ammonia, but it seems to me it is clearly being caused by the severe and sudden drop in carbonates.

Last night I was just bewildered by the change. This morning it occured to me that I was always testing water off the top of the tank. Because of the planned CO2 injection, there is virtually no surface agitation. For all of the filters the uptakes and outputs are at opposite ends of the tank, all uptakes on one end and all outputs on the other, to keep the water moving without agitating it. I understand that carbonates are dissolved into the water, not little particles floating in it, but could the carbonates have settled to the bottom of the tank? When I get home I will test using water near the dispersion bars, but I am very confused. Do carbonates settle? If not, where did my carbonates go!?
 
You're a little off on KH. KH is the measure of calcium, magnesium, and other hard ions in relation to carbonate and bicarbonate in water. It is also referred to as permanent hardness. You are correct in your assumption that the level of KH should not fluctuate as it has in your tank. I'm a bit confused by this as well.
 
Quick update:

Went on lunch break and tested the water at several different depths and places in the tank. Still getting less than one degree Kh. Filled a cup with tap water and put in some water conditioner (API stress coat) to see if that would affect it, it didnt. Tap water and tap water with water conditioner still showing 7 dKh.
 
Yeah, as far as I know, there are only two ways to drop KH levels:

boiling water
reverse osmosis

You have a very interesting situation.
 
Hawkfish3.0;1921200; said:
You're a little off on KH. KH is the measure of calcium, magnesium, and other hard ions in relation to carbonate and bicarbonate in water. It is also referred to as permanent hardness. You are correct in your assumption that the level of KH should not fluctuate as it has in your tank. I'm a bit confused by this as well.
Click to expand...


KH is "carbonate" hardness and is essentially the buffering capacity due to the presence of carbonate and bicarbonate. It is temporary and will fluctuate over time due to the progressive acidification of the tank.

GH is "general" hardness. It is due primarily to calcium and magnesium and exhibits much greater stability over time.

"Total hardness" = KH + GH

Perhaps you just got your terms mixed up.
 
strong acids will lower Kh as well as the two ways you mentioned. By strong I mean a type of acid that falls in the 'strong acids' category vs the 'weak acids' category, not 'acid that will totally melt you'. Strong vs. Weak acid has to do with how they react. the acid formed when CO2 and water mix is a weak acid, it will lower Ph without lowering Kh. humic acids (peat) and nitric acid (nitrate) will lower Kh. The problem is, the water has not come into contact with peat, and 24 hours of 12 zebra danios and uncycled filters in 125 gallons is nowhere close to enough to produce the biblical amounts of nitrate it would take to lower Kh by 7 degrees.
 
brianp;1921674; said:
KH is "carbonate" hardness and is essentially the buffering capacity due to the presence of carbonate and bicarbonate. It is temporary and will fluctuate over time due to the progressive acidification of the tank.

GH is "general" hardness. It is due primarily to calcium and magnesium and exhibits much greater stability over time.

"Total hardness" = KH + GH

Perhaps you just got your terms mixed up.
Click to expand...

:duh: You are correct sir!
 
rye;1921703; said:
strong acids will lower Kh as well as the two ways you mentioned. By strong I mean a type of acid that falls in the 'strong acids' category vs the 'weak acids' category, not 'acid that will totally melt you'. Strong vs. Weak acid has to do with how they react. the acid formed when CO2 and water mix is a weak acid, it will lower Ph without lowering Kh. humic acids (peat) and nitric acid (nitrate) will lower Kh. The problem is, the water has not come into contact with peat, and 24 hours of 12 zebra danios and uncycled filters in 125 gallons is nowhere close to enough to produce the biblical amounts of nitrate it would take to lower Kh by 7 degrees.
Click to expand...

One thing I would add as a concern here; do you plan on keeping the tank planted? I assume so, since you're doing CO2 injection.

The only problem with CO2 injection is that it will lower your carbonate hardness, reducing your buffering capacity. In consequence, your pH levels may become unstable.
 
you assume correctly indeed, it will be heavily planted.

I do not want to be argumentative, I appreciate any and all suggestions, and I could be misunderstanding my research, but from what I understand, weak acids do not affect Kh. They will lower Ph, the drop in Ph is more dramatic the lower the Kh is, but weak acids themselves do not affect Kh. Carbonic acid, the acid formed by CO2 and water, is a weak acid, and should not affect the Kh. What I mean by example is if water has a Ph of 8 and a Kh of 10 and a low level of CO2, you could add a lot CO2 and lower the Ph to 7, but the Kh would still be 10. If you then quit adding CO2 and let the excess dissolve out, the Ph would shoot right back up to 8 because the Kh remained unchanged. I beleive this is why the charts that estimate CO2 based on Kh and Ph are able to be fairly accurate.

The water is right out of the tap, its temp hasnt risen above 79 degrees, so all I can think of is that somehow some strong acid must have gotten in the tank. On the decorations or in the substrate or something. Either that or there is a way to lower Kh besides purified water, boiling, or strong acids. I just cant figure it out.

The fish I plan to keep in it are soft acidic water natives, so lowering the Kh and Ph of the tap water, both of which are pretty high, is probably a good thing, but it has gotten too low and according to the CO2 calculator I have, to hit 20 ppm CO2 I would drop the Ph to around 5! Not to mention the fact that having no buffer whatsoever the nitrates and Ph swings could get ugly fast. If I could find out why my Kh dropped so far and control it, lowering it somewhat, just not this far, it could actually be a real boon to the tank.
 
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