RODI Water, proper CO2 levels, & pH Controllers - The Planted Tank Forum
 
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post #1 of 14 (permalink) Old 05-25-2015, 04:27 PM Thread Starter
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RODI Water, proper CO2 levels, & pH Controllers

I'm feeling like I need to start over with all I know in regards to proper CO2 levels in my planted tank. Quick rundown: I have a 115 gal tank with Instant Aquariumo sand substrate, filled with 30% tap water/70% RODI water, co2 injection and a pH controller.

My fish are currently in the quarantine tank while I make sure the set up is suitable for them (16 Discus) that being said -- The problem is that how do I ensure the water has the correct level of co2 for my plants? pH is currently at 6.6 with the controller set to come on if levels hit above 6.9 ... Please advise me...lol

100 Gal Tank
Lights:
  • 2x Fluval LED (8 hours) &
  • 1x Current Satellite LED (10 hours)
Co2 Injected
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post #2 of 14 (permalink) Old 05-25-2015, 05:18 PM
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You could use a drop checker, but perhaps easier is to allow your tank to de-gas all the CO2 (ie turn off CO2 after lights out), and then take a baseline pH measurement in the morning. Increasing surface agitation will help speed up the de-gas process. The next morning (depending on the agitation) the pH will stabilize at its highest value. It is generally accepted that you have about 3ppm of CO2 in the tank at this point.
Now you want to raise your CO2 levels to about 20-30ppm. With a pH controller you simply set the target to be 0.8-1.0 lower than your pH baseline, and the CO2 will turn off at around 20-30ppm (0.8 drop might get you to 20ppm CO2, and a drop of 1.0+ will get to you around 30ppm CO2).

When you introduce your discus, repeat this process, and make sure they are not stressed as the CO2 levels rise. You may not be able to get the full 30ppm with discus.

Bump: Question ... is CO2 even running now, given the controller is set to 6.9?

Last edited by imcmaster; 05-25-2015 at 05:22 PM. Reason: Is CO2 even on?
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post #3 of 14 (permalink) Old 05-25-2015, 07:35 PM Thread Starter
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Quote:
Originally Posted by imcmaster View Post
You could use a drop checker, but perhaps easier is to allow your tank to de-gas all the CO2 (ie turn off CO2 after lights out), and then take a baseline pH measurement in the morning. Increasing surface agitation will help speed up the de-gas process. The next morning (depending on the agitation) the pH will stabilize at its highest value. It is generally accepted that you have about 3ppm of CO2 in the tank at this point.
Now you want to raise your CO2 levels to about 20-30ppm. With a pH controller you simply set the target to be 0.8-1.0 lower than your pH baseline, and the CO2 will turn off at around 20-30ppm (0.8 drop might get you to 20ppm CO2, and a drop of 1.0+ will get to you around 30ppm CO2).

When you introduce your discus, repeat this process, and make sure they are not stressed as the CO2 levels rise. You may not be able to get the full 30ppm with discus.

Bump: Question ... is CO2 even running now, given the controller is set to 6.9?
Firstly, thank you so much for the in-depth explanation.

As for if my co2 is running, it's definitely not. the pH is at 6.7 currently, which I'm fairly certain is the baseline, but I want to wait until the AM to be completely sure. The main thing is that I wanted make sure i understood the relationship between the pH and c02 correctly.

That being said, so if 6.7pH ends up being my baseline and I want 20ppm, my pH would be 5.9? And is this safe for the Discus (and other fish because I want to add in some Apistos) with such a low pH?

100 Gal Tank
Lights:
  • 2x Fluval LED (8 hours) &
  • 1x Current Satellite LED (10 hours)
Co2 Injected
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post #4 of 14 (permalink) Old 05-25-2015, 08:10 PM
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That is correct. If your baseline is 6.7, then a pH of 5.9 would suggest that your CO2 level is about 20ppm.

I hope discus keepers will chime in here. I have read discus like the pH around 6.0+. I am pretty sure for apistos you can go well below 6.0.

Have you considered mixing in a bit more tap (maybe 60% RO / 40% tap) to get your pH a bit higher, if you are concerned your ph is going too low)? What is your gH? I guess you are also trying to mix RO for very soft water.
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post #5 of 14 (permalink) Old 05-26-2015, 11:20 PM Thread Starter
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Quote:
Originally Posted by imcmaster View Post
That is correct. If your baseline is 6.7, then a pH of 5.9 would suggest that your CO2 level is about 20ppm.

I hope discus keepers will chime in here. I have read discus like the pH around 6.0+. I am pretty sure for apistos you can go well below 6.0.

Have you considered mixing in a bit more tap (maybe 60% RO / 40% tap) to get your pH a bit higher, if you are concerned your ph is going too low)? What is your gH? I guess you are also trying to mix RO for very soft water.
Im going to take your suggestion and mix a little treated tap water with my RODI water. Last night when I set the filter to cause surface disturbance the pH went up to 7.0. I'm having a really big fight with Nitrites right now for some reason but thats a whole other issue...

the main thing is I didn't know the correlation between pH and co2 ppm... and how the pH controller could help me with this
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post #6 of 14 (permalink) Old 05-27-2015, 02:36 AM
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Take some tank water, put it in a small container/bucket/whatever, put an air stone in it. Wait an hour then test pH.

This pH is the pH of your tank water without CO2 (the air stone degassed it all). To add 30ppm of CO2, set the pH controller for a 1 pH drop. So if the tank water without CO2 is 7.3 pH, set the pH controller to 6.3 pH.

A higher pH with your controller (above 6.3 in the example above) would mean less CO2 in the water, and a lower pH (below 6.3 in the example above) would mean more CO2 in the water.
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post #7 of 14 (permalink) Old 05-30-2015, 02:55 AM Thread Starter
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UPDATE
Whoa! The 'Air stone for an hour' method worked really well..!!!

A few days ago to find the baseline, I aimed the filter spout at the surface of the water to create ripples. I did this overnight and came with a baseline of 6.9 -- BUT when I used the airline/air-stone and checked the pH after an hour, the pH was actually 8.0!!!

It explains why when I tried to acclimate my fish they went crazy and I had to scoop them out really fast and put them back in quarantine! I had the controller set at 6.1

100 Gal Tank
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  • 2x Fluval LED (8 hours) &
  • 1x Current Satellite LED (10 hours)
Co2 Injected
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post #8 of 14 (permalink) Old 05-30-2015, 03:26 AM
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Taking the water out of the tank stops any factors from the tank affecting the results. I use a 2 litre coke bottle with the top cut off, and have a large airstone that just fits into the coke bottle. This means lots of surface agitation, and I off gas the CO2 in less than 5 mins.

With a pH of 8.0, you could aim for a safe CO2 level by driving the pH down to 7.0. I like to base the results from KH though. My baseline pH is 8.1, but with KH 5, I drive my pH down to 6.7-6.8 based on the CO2/pH/KH table: http://www.barrreport.com/forum/barr...o2-ph-kh-table

If I experiment by trying to drive the pH down any further, some of the fish start reaching for the surface. I think I'm going to settle for pH 6.8.

Last edited by Audionut; 05-30-2015 at 11:36 AM. Reason: drive down pH, not CO2
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post #9 of 14 (permalink) Old 05-30-2015, 05:06 AM Thread Starter
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Originally Posted by Audionut View Post
...With a pH of 8.0, you could aim for a safe CO2 level by driving the pH down to 7.0. I like to base the results from KH though. My baseline pH is 8.1, but with KH 5, I drive my pH down to 6.7-6.8 based on the CO2/pH/KH table: http://www.barrreport.com/forum/barr...o2-ph-kh-table

If I experiment by trying to drive the CO2 down any further, some of the fish start reaching for the surface. I think I'm going to settle for pH 6.8.
Yeah with Discus, I have to be extremely careful. I just checked and the pH is 8.3 with a kH of 8. So according to the barr report I should aim for a pH of 6.9 or 6.8?

100 Gal Tank
Lights:
  • 2x Fluval LED (8 hours) &
  • 1x Current Satellite LED (10 hours)
Co2 Injected
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post #10 of 14 (permalink) Old 05-30-2015, 05:15 AM
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I'd start at 7.3 (lowest). Get the fish in, let them settle, and then start going down further.
Go down slowly, and as soon as you see them laboring or reaching for the surface, back it off a little.
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post #11 of 14 (permalink) Old 05-30-2015, 08:31 AM Thread Starter
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Sounds like a good plan. I was thinking of trying to go down .1 per day from the 7.3 mark. I may also do a large water change (again) tomorrow so that I can have a lower baseline before introducing the fish to the aquarium. With this, it should allow for a lower pH right? (I read that discus like a pH of 5.0-6.5)
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post #12 of 14 (permalink) Old 05-30-2015, 11:06 AM
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There's a limit of CO2 fish can tolerate, regardless of pH. You'd need to lower KH to have a lower pH for the same CO2 level.

That's my understanding of it anyway, I haven't had a chance to test my understanding of it yet.
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post #13 of 14 (permalink) Old 06-18-2015, 07:46 AM
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Any updates?

I've lowered my KH to 3 and dropped pH to 6.55. Will try going down to 6.45-6.50 tomorrow.
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post #14 of 14 (permalink) Old 06-18-2015, 04:28 PM
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Please forgive my ignorance here as I am very new to high tech planted tanks...

This thread has intrigued me as I am curious how the pH manipulation effects the bacteria consuming nitrogen compounds, or is it moot since the idea is the plants remove enough NH3/NH4 on their own?

My understanding of pH with regards to nitrospira, nitrosomana and nitrobacter is that as pH decreases so to does the efficiency of the bacteria's consumption of the nitrogen compounds. At 5.5 pH the bacteria become dormant.

Oh boy, this hobby gets more complex the more I learn! I love it!

I learned the hard way that I am only a water keeper!
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