Interrelated parameters confusing - The Planted Tank Forum
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post #1 of 4 (permalink) Old 11-25-2016, 06:53 PM Thread Starter
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Question Interrelated parameters confusing

So, our tap water is 10 dkh. It has a degassed pH of 8.2. I have been looking at the relationship between pH and KH. We have a strong light and, as I understand it, that means that we should get our CO2 in the 30 parts per million range. This raises all kinds of questions.

1. With injected CO2, do we worry about a pH swing every night? I am not using, nor do I want to use, a pH controller. If I provide a significant amount of injected CO2 during the photo period to balance my high lights, and then if gas is turned off during the night, are not significant pH swings created that are harmful to fish? I measured my tank just before my CO2 kicked on today, and it was 8.2.

2. Is the drop Checker useful to me considering that the solution KH is 4? It seems that if I shoot for a green drop checker (reflecting a pH of 6.8), I will be shooting for a pH that is significantly different than the normal pH of my water when it is degassed (8.2). So, should I adjust the dkh of my drop checker solution to be more in line with my water hardness?

3. What is the best approach with surface agitation, given my goals of not wanting to see large pH swings as CO2 is off gassed, but also not wanting my fish to die of oxygen deprivation when I need to give large doses of CO2 and also have them survive the night when no CO2 is being injected, but when CO2 is high from having been injected during the entire photo period? My tank is a 120, and I run two Eheim 2217s on it. I have a gentle ripple in my tank surface water going now. The spray bar is positioned about 2 inches under the surface pointing slightly toward the surface and toward the front of the tank.

4. Is the term "stable CO2" related to a stable pH level 24/7, or more related to a stable amount of CO2 put into the water table daily? I've read it both ways, and I'm confused.

So, to sum up, what is the best balance (stability?) that I can work to achieve between my higher dkh, my higher pH, my drop checker, and my surface agitation (or, more importantly, oxygenation for fish health)?

Tanks a bunch!

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post #2 of 4 (permalink) Old 11-25-2016, 07:26 PM
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Quote:
Originally Posted by Tanks! View Post
So, our tap water is 10 dkh. It has a degassed pH of 8.2. I have been looking at the relationship between pH and KH. We have a strong light and, as I understand it, that means that we should get our CO2 in the 30 parts per million range. This raises all kinds of questions.

1. With injected CO2, do we worry about a pH swing every night? I am not using, nor do I want to use, a pH controller. If I provide a significant amount of injected CO2 during the photo period to balance my high lights, and then if gas is turned off during the night, are not significant pH swings created that are harmful to fish? I measured my tank just before my CO2 kicked on today, and it was 8.2.


PH swing caused by CO2 injection will not hurt the fish , My KH is at 4 and with a ph drop of one full point ( 7.1 to 6.1 ) CO2 levels are 300ppm

2. Is the drop Checker useful to me considering that the solution KH is 4? It seems that if I shoot for a green drop checker (reflecting a pH of 6.8), I will be shooting for a pH that is significantly different than the normal pH of my water when it is degassed (8.2). So, should I adjust the dkh of my drop checker solution to be more in line with my water hardness?

3. What is the best approach with surface agitation, given my goals of not wanting to see large pH swings as CO2 is off gassed, but also not wanting my fish to die of oxygen deprivation when I need to give large doses of CO2 and also have them survive the night when no CO2 is being injected, but when CO2 is high from having been injected during the entire photo period? My tank is a 120, and I run two Eheim 2217s on it. I have a gentle ripple in my tank surface water going now. The spray bar is positioned about 2 inches under the surface pointing slightly toward the surface and toward the front of the tank.


If you are shooting for 30ppm of CO2 and your tank temp is 80-86 , then you should have a strong surface movement rippling , but not to the point it breaks the surface. I have a air bar at the bottom back of my tanks , they are timed to come on when lights and CO2 go off.

4. Is the term "stable CO2" related to a stable pH level 24/7, or more related to a stable amount of CO2 put into the water table daily? I've read it both ways, and I'm confused.


Stable CO2 means it should be at our target PPM (30ppm ) when the lights come on and stay at that level until lights go out

So, to sum up, what is the best balance (stability?) that I can work to achieve between my higher dkh, my higher pH, my drop checker, and my surface agitation (or, more importantly, oxygenation for fish health)?

ttt
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post #3 of 4 (permalink) Old 11-25-2016, 07:53 PM
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1. Dont worry about the PH drop from CO2, it doesnt hurt anything. The harmful effect on livestock from too much co2 has to do with respiration, not PH

2. Drop checker solution has nothing to do with your tank water parameters, use the 4 dKH solution. It will turn green with roughly 30 ppm.

Drop checkers are good for a general approximation, but it's better to measure the relative PH drop between de-gassed tank water and water with the CO2 on. De-gassed means water that's been sitting out for 24-36 hours to let all the CO2 "degas."

This will require a digital PH pen, cant use dip sticks or liquid tests. You can get one for less than $20 on amazon, and you'll need to buy calibration solutions for it as well.

Ideally you should have a full 1 point drop by the time the lights come on, or shortly thereafter.

You'll need to work it out so you have enough in the beginning (at lights on) but it doesnt become too much later on in the day, as the CO2 concentration increases.

A 1.2 drop or so at peak levels is usually OK, but pay attention to your livestock and watch for signs of discomfort.

If the co2 becomes too much later on, then try starting the CO2 earlier, at a lower rate, say 2 hours before the lights come on, etc. A particular rate of CO2 will eventually reach a peak concentration and stay there, it is not a never ending climb. So with a lower rate starting earlier, it'll take longer to build up (drop the PH) but the peak levels will be lower.


3. Surface agitation is good. It allows gaseous exchange with the atmosphere which provides better O2 levels, among other things. It will also allow your livestock to be comfortable at higher levels of CO2.

Turn the CO2 off maybe 30 minutes or an hour before the lights go out and dont worry about the PH. Have the CO2 come on an hour or two before the lights, as mentioned above.

4. Stable CO2 means consistent levels of dissolved CO2 in the water column. Again, nothing to do with PH.

To reiterate, PH swings from CO2 are not harmful to livestock. Swings in GH or KH can be, but CO2 alone does not affect either one. CO2 becomes a problem by affecting livestock's ability to "breath" which has nothing to do with PH.
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post #4 of 4 (permalink) Old 11-25-2016, 08:11 PM Thread Starter
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Thanks, both of you. I'm hoping it will all come clear soon! :-)

Tanks a bunch!

My current 120 tank journal:
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