PH Low - CO2 wont cut in - Where should I look?

Aftica

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Mar 14, 2005
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Tom Barr;13270 said:
Gievn the wide variety of user error in KH measurements, I've asked Greg at SeaChem if they might be so kind to make a reference KH solution that is accurate to less than 1ppm for the hobbyist.

Ok - I made the 4 dKH water test solution and the test kit (Hagen) did measure pretty darn close... at 7 drops it was almost color changed - you know when you hit that stage when you can tell with 100% certainity that the next drop will be the one... and 8 drops did it.

So my kit tests the 4º solution at between 3.92º and 4.48º KH - to me thats good enough.

So getting back to the origional reason for the thread.. something has dropped my KH from about 100ppm to less than 10ppm in my tank... this in turn now keeps my pH down around 5.5 and my GH has remained relativly unchanged.

:confused: Still open to any suggestions as to a good course of action to get this back on track?
 

Frolicsome_Flora

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Wouldnt 50% weekly water changes replace any loss of KH pretty regularly? It seems odd to think that plants would be able to absorb that much in such a short time.

One other thing, are you sure that the reactor is working properly? I have one of the smaller versions of the one your using and its pretty awful.
 

Aftica

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Reactor works perfectly when the CO2 comes on....but... since the CO2 don't come on - the reactor is not utilized.

CO2 is really not the issue... KH is. If I actually hauled out the ole Lamotte CO2 test kit I'd be willing to bet that there is very little CO2 in the water, despite what the chart says..

So whatever caused my KH to drop is my problem. With little buffering < 1º dKH, any acid will lower pH drastically such as acidity produced by nitrification My thinking is that the mulm, dead vegetation in the flourite bed etc... is acting like filtering the water over peat - the carbonate ions or KH is being used up and thus my PH dropping without the benefit of injected CO2....

A through vacuuming of the substrate I think is in order... and increase the Water changes from 20% to perhaps 40% weekly for a while....?
 

aquabillpers

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Before you disturb the substrate, why not add some sodium bicarb, enough to bring the KH up to 5 to 10 degrees. Measure the KH after it dissolves, then measure it again after a day or two.

A second point: My impression is that aged mulm is almost chemically inert, so it wouldn't have much effect on pH. I'd like an opinion from an expert on this, though.

Bill
 

Aftica

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aquabillpers;13291 said:
Before you disturb the substrate, why not add some sodium bicarb, enough to bring the KH up to 5 to 10 degrees. Measure the KH after it dissolves, then measure it again after a day or two.

A second point: My impression is that aged mulm is almost chemically inert, so it wouldn't have much effect on pH. I'd like an opinion from an expert on this, though.



Adding the sodium bicarb would be one way - and measuring it a few days later and seeing what happens etc... however I do have Discus and cardinal tetras in here... kinda fearful of fast raising and falling of PH/KH... kinda like to address the cause first...

Aged Mulm is chemically inert? well - if that is true it would throw my theory out the window... be interesting to see what others say on that.. I figured it to be the opposite - like my peat analogy...
 

Sintei

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VaughnH;13258 said:
Add 4.99 grams of bicarbonate of soda, after drying it in an oven at about 250F or whatever the lowest setting of the oven is, for a half hour or so, to 5 liters of distilled water. That gives you 40 dKH water. Then mix 10 ml of that 40 dKH water with 90 ml of plain distilled water. That gives you 4 dKH water. With this you can calibrate your KH test kit, as well as load a drop checker.
Sintei;13261 said:
Question:

Why bother drying it in the oven? Is there so much fluid in it it will affect meassurment?
Ill test it in my lab tomorrow if i get time for it..

Well i tested it and look and behold, there was roughly 1% dissipation up to 67 Celsius degrees. Then my program shut down (no difference meassured within a certain time interval.) Obviously all water would be gone at 100 C degrees and another dissipation factor would be. Though i had no time to rewrite the program.

Conclusion, drying in an oven is needed to get accurate KH. :)
 

Frolicsome_Flora

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VaughnH;13258 said:
Add 4.99 grams of bicarbonate of soda, after drying it in an oven at about 250F or whatever the lowest setting of the oven is, for a half hour or so, to 5 liters of distilled water. That gives you 40 dKH water. Then mix 10 ml of that 40 dKH water with 90 ml of plain distilled water. That gives you 4 dKH water. With this you can calibrate your KH test kit, as well as load a drop checker.

Vaughn: I did this and Im pretty amazed my CO2 is so low, only 9ppm *boggle* I dont think Im ever going to trust a test kit again! I tested the 4dKH water with my nutrafin kit and it read only 2dKH, kit is only 3 weeks old too.

Thanks for this info, Ive ordered a proper pressurised CO2 kit which should be here in the next few days, then maybe I can get things stable.
 

VaughnH

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Don't forget just how difficult it is to get an accurate measure of CO2. A very small error in pH makes a big difference in the calculated amount of CO2, and a 20% error in KH makes a 20% error in the calculated amount of CO2. So, I have been trying to change our culture to where we refer to our CO2 concentration as "30-40ppm" or "5 - 20 ppm", instead of 31.8 ppm and 11.4 ppm. We really have no way to get much closer than that, without some well calibrated lab equipment. I mention this because you noted that you have 9 ppm of CO2. I would say you have between 5 and 20 ppm.