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Discussion Starter · #1 ·
I'm having a problem with my CO2 and would appreciate any input you might have. I'm also hoping this isn't a stupid question :smile: I have a 85G planted discus tank with a controller-maintained pH of 6.8 (full tank stats below). The CO2 set-up does work properly, but it seems that during the day, the CO2 is rarely flowing. Shouldn't it be running most of the day with the lighting cycle? When it is flowing (seems rare), the pH will drop quickly. For example, it takes less than 10 minutes fo the tank to go from 6.8 to 6.5, if I dial the pH setting on the controller down a bit. Is this normal?

Based on other posts, it sounds like people run their systems non-stop with the lighting cycle. I realize that my controller set-up operates a little differently, but I'm not sure that I'm getting enough CO2 into the tank. Based on the CO2/KH/pH table it looks like I should have a good level (23.7 ppm), but I don't understand how this can be the case if my bubble counter is standing still everytime I look at it :-s

Any thoughts?

I'm partly skeptical because the CO2 does not seem to have impacted my heavy BBA and green spot algae. The CO2 system is about 2 months old now.

On a separate note, I just emailed a request to join SFBAAPS. I'm looking forward to meeting with you guys in the near future. Thanks,

Jim

85G planted discus tank
Milwaukee pressurized CO2/pH controller/power reactor/
CO2 flow rate is 2 bubbles per second
KH: 5
GH: 7
TDS: 210
Combination of RO water and tap (in the process of moving to all RO to control extreme PO4 levels and hardness)
Fluval 404 canister filter
84 degrees
JBJ PC lighting, 3.0 wpg, 12 hours per day
Substrate is small to medium-sized gravel and Flourite
Fish load is moderate to heavy
Plant load is moderate
Greg Watson ferts: CSM+B+Fe (10ml 3x week), KNO3 maintained between 5-10 ppm, not currently dosing PO3 because existing levels in water are high (more than 5 ppm)
 

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If your CO2 is dropping the pH that rapidly it may just be that the solenoid is cycling for very short periods of time and you are just missing the cycle. So long as your pH level is at your target setting I wouldn't worry, but I would decrease your bublle rate so that the pH change isn't so swift.
 

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Do you use a sump tank? How far is your CO2 reactor output from ph probe? Do you notice your solenoid going on/off frequently(you hear a click sound every time it goes on/off)? Did you turn your CO2 bubble rate really high(so ph drops really fast when solenoid turns on)? Have you calibrated your ph controller recently, at least did a sanity check comparing to a test kit? I am seeing some warning signs here. It is time to fine tune your needle valve and turn it down a notch. I hope you use necessary precautions so that no CO2 disaster every happens. You probably have read the recent ph crash thread on the general forum on PT forums, it would be a devastating loss.

Out of all the possibilities, my best guess right now, is that your ph controller calibration is off, that is, ph is not as low as it shows. and you are not getting enough CO2.

FYI, in my 100gallon discus tank. kh=4, ph=6.7-6.8 with ph controller. ph=7.4 before I turn on solenoid with a timer(I shut if off at night). Takes 1.5 hours to reach target.

Hope to see you at the SFBAAPS plant swaps. :)
 

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Discussion Starter · #4 ·
No, I'm not using a sump tank. The CO2 reactor is pretty close to the probe -- above the reactor probably 6" away. Should I move the probe to the other side of my tank?

The solenoid does appear to be working properly, but I do not hear it going on/off frequently.

I don't think the bubble rate is high -- 2 per second. Please let me know if you disagree. I have not calibrated the controller since setting it up two months ago. Will do.

Thanks for the replies,

Jim
 

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I use a sump wet/dry. Initially I had the probe in the sump along with CO2 reactor. My solenoid would go on/off very frequently because the probe is too close to the CO2 rich outlet. So I moved the probe to the overflow prefilter. Sounds like you don't have that problem. Still, I suspect your calibration might be off, it is easier to drop ph initially when CO2 is low.
 
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