PH lowering

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ddoan

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Aug 17, 2003
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I had a slight PH and KH problem with a substrate, so instead of tearing down the tank, I added HCl. I added roughly 300 ml to a 15 gallon tank and the PH plummeted and took the KH with it. I'm sitting and testing it and I get a stable PH of 6.8 and a KH of 17.

Here's my question, as a by product of the reaction Cl- is formed, if I added declorinator to the tank, would that get rid of the Cl-?

The tank seems to be stabilizing and hopefully I have exhausted all the CO3 from the substrate. I probably will raise the PH slighly with buffers.
 

IndianaSam

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Mar 13, 2004
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Originally posted by ddoan
Here's my question, as a by product of the reaction Cl- is formed, if I added declorinator to the tank, would that get rid of the Cl-?
Nope, at least I don't think so. You just have Cl- ions in your water now. Chlorine is Cl2.

Why did you add that much HCl? 300mL seems like a lot to me. Do you know its molarity (concentration)?
 

ddoan

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The bottle says 20 Be, anyways, I had a high CO3 concentration and had to get it down, so I added enough to get the reaction going and eliminate as much CO3 as possible, or bring it down to a suitable level.

Is there a way to remove the Cl- ions or is just doing a water change the only way?
 

happychem

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Dec 9, 2003
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It probably would have been easier to have done this prior to setting up the tank. What is your substrate? How high were your KH and pH?

I'm not familiar with "Be" as a conc. term, are you sure there's no percentage on the bottle?

There is no way to remove Cl- ions other than water changes. However, depending on the concentration of the HCl you added, you probably don't have to worry about it. You've got about 60L of water in your tank, I think, so if the HCl conc. was on the order of 10% (which is pretty high if you back calc. to molarity), you'll have (order of magnitude) 0.0005% Cl, or 0.005ppt, so a good 50% water change.

But back to the original question, why this undertaking? What were these KH/pH values that were so high to begin with?
 

ddoan

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The pH hovered around 8.8+ and the KH was at 800 ppm at one point. I was able to get the ph down to 6 and the kh down to 100 ppm and keep it there within 24 hours.

But the KH slowly goes up again and so does the ph which is a good sign, because it looks like I am exhausting the CO3 levels at this rate and it has only been 2 days.

I really dont want to take down the tank again hence why I am doing this.

Here's a question, does the water make contact with all the sand in the tank? I'm stiring up the sand as I do this just be safe that all the substrate is exposed to HCl.
 
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