Dramatic PH change with substrate - The Planted Tank Forum
 
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post #1 of 14 (permalink) Old 02-10-2005, 06:08 AM Thread Starter
 
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Dramatic PH change with substrate

I originally put some Home Depot pea gravel in my 10 gallon and my Ph was 7.8. Recently I changed it to sand and retested, now it's 6.9. That seems like a dramtic change.

My KH is at 3 and GH 2 with the sand.

I bought a hagen Co2 kit and will purchase starter plants soon. What important information are these three readings telling me regarding Co2?

Im not sure what this chart is telling me https://www.plantedtank.net/forums/sh...ad.php?t=14103
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post #2 of 14 (permalink) Old 02-10-2005, 06:26 AM
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It's telling you your CO2 levels are on the low side just a bit from the optimal range.

The formula is:

CO2 (in PPM) = 3 * KH * 10^( 7-pH ) and since I can't find my calculator and it's been a long day, I'll let you do the math
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post #3 of 14 (permalink) Old 02-10-2005, 06:30 AM Thread Starter
 
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I haven't even taken the Hagen unit out of the box yet and the chart is telling me I have 15ppm c02, doesn't seem possible.

Is Red Star Active Dry Yeast good enough to use?

With my readings should I be using baking soda in the mix?

Last edited by Ahkuma; 02-10-2005 at 04:48 PM.
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post #4 of 14 (permalink) Old 02-10-2005, 06:39 AM
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Wow !!! I didn't know the hagens were THAT good

I believe the chart assumes supplemental CO2, I'm not a chemist, but I'm not sure if it indicates any CO2 in your case, but we have a few forum members who are definitely qualified to answer that.

However, the pea gravel could have been buffering your water to some extent and sand isn't which could account for the pH drop. Plants will also extract elements from the water column which would also lower your pH.
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post #5 of 14 (permalink) Old 02-10-2005, 12:53 PM
 
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like gg said it could be the substrates.. 'possibly' either the gravel was inert or the sand is either way one or the other was putting the ph up by adding elements to the water. have u tried testing your tap water to see what the ph of that is then maybe you will know which has caused the swing. what was the gh before you added the sand?

imo its best to stick with a substrates that wont alter your ph.. what sort of sand are you useing.. it seems like the gravel was the problem but again that depends on what the water is to start with. post your tap water physics mate. ph, gh,
another thing.. co2 will exsist in the tank regardless of whether you add it or not, the fish and bacteria all produce co2 so there will be some tini traces
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post #6 of 14 (permalink) Old 02-10-2005, 01:13 PM
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You are all missing the point. Ahkuma is/was not using CO2 yet. Also with a kH of 3 you would expect a pH of around 7.6.

If the sand is affecting the pH then it must contain something acidic to LOWER the pH.
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post #7 of 14 (permalink) Old 02-10-2005, 01:21 PM
 
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i know he isnt dosing co2 he said that above... but we dont know whats effecting what because he hasent posted ph and gh for tap water, sand water and gravel water... if you see my point? he says the ph of the gravel to sand.. but he doesent say the hardness before the gravel was removed.. nor the kh with the gravel.. and he doesent state the ph or gh of any water before it enters the tank.. something i consider to be the rock bottom of getting your head around one of these situations.. thats all im saying but i do know he isnt dosing co2
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post #8 of 14 (permalink) Old 02-10-2005, 04:59 PM Thread Starter
 
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I took the gravel out of the tank before I ever tested the GH/KH but I still have a bunch of it outside in a bag so I will test my tap water and the pea gravel today.

The sand I bought was from a local fish store and in one of the bins that was supposedly pure with nothing added.
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post #9 of 14 (permalink) Old 02-10-2005, 07:29 PM
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Quote:
Originally Posted by glass-gardens.com
Wow !!! I didn't know the hagens were THAT good

I believe the chart assumes supplemental CO2, I'm not a chemist, but I'm not sure if it indicates any CO2 in your case, but we have a few forum members who are definitely qualified to answer that.

However, the pea gravel could have been buffering your water to some extent and sand isn't which could account for the pH drop. Plants will also extract elements from the water column which would also lower your pH.
Chemist reporting for duty.

I'm with rex. If you had a bucket of pure water at that kH/GH the pH should be much higher. The chart tells the maximum CO2 that will dissolve assuming carbonate buffering so use it with caution. Kinda like a econobox car with a speedometer that goes up to 120 MPH... Therefore, there is something else in the water causing a problem. I agree with compulsion in that it would be nice to have values for all three combos (add water to clean glass jugs with substrate, let sit at least overnight to reach equilibrium, test. Wait another day, test and see if it moves.) The thing I do not understand is what contaminate in sand would lower pH. My understanding is that you often get shell which raises pH (through KH/GH.) I thought plants extracted bicarbonate which raises pH.

Moved to Tucson.
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post #10 of 14 (permalink) Old 02-10-2005, 08:13 PM Thread Starter
 
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Blue Ram,

Currently the test is being conducted in two, giant, plastic, Sea World cups with Shamu on them. I noticed in your post you made a point to mention glass containers. Should I start over?
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post #11 of 14 (permalink) Old 02-10-2005, 08:25 PM
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Quote:
Originally Posted by Ahkuma
Blue Ram,

Currently the test is being conducted in two, giant, plastic, Sea World cups with Shamu on them. I noticed in your post you made a point to mention glass containers. Should I start over?
I am not sure. I was thinking glass because it is more inert but your cups do have Shamu on them so that has to be worth something. Comments anyone? Can you do three cups (Tap, new stuff in tap (tank water???), old stuff in tap?)

Moved to Tucson.
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post #12 of 14 (permalink) Old 02-11-2005, 04:06 AM
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I have a theory. Perhaps the pea gravel had some CC in it and the sand is inert. Therefore, the water returned to a more balanced 6.9 once the buffering gravel was removed. How long had that gravel been in there? Also, all is mute, till we know what you standing pH is. Maybe 24 hours standing would be nice. Just a theory. bob





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post #13 of 14 (permalink) Old 02-11-2005, 04:30 AM
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Betowess:

I agree that the sand is likely the more inert of the two (CC=crushed coral?) That would explain why the gravel was high but I am more interested in why the new stuff is low. Since the carbonate CO2 table is based on the assumption that you only have carbonate buffers, I would like to know what might be in their tank. Like rex posted, the pH should be 7+. Either I need to think about exactly why peat/rotting stuff drops pH or grab a pencil and pull out my chemistry text.

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post #14 of 14 (permalink) Old 02-12-2005, 03:46 AM
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Yeah, I meant calcium carbonate or crushed coral and the like. When I first started out, I had all kind of problems with my soft well water because I wasn't measuring the "standing" pH and was putting in baking soda and watching 6.9 pH go up to 7.9 after a couple of days. My greenhorn mistake. So I think there's probably something in the gravel, but its just a hunch.





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