Sedra 9000 Needle Wheel CO2 Injection

travis

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Aug 30, 2006
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I recently set up a client's 125G w/sump using a Sedra 9000 Needle Wheel pump (900 GPH @ 13' Head) for return (3/4" split into two return lines). The pump does a great job with water flow, even with the needle wheel's lower than spec GPH performance, and it fills the tank with an incredible CO2 mist, but the client reports that he is unable to drop the pH below 6.8 (KH 2-3). I need to hit a pH of 6.3 or 6.4 to feel comfortable with CO2 levels in this tank.

I'm going to be checking the install out this week and thought I would run this issue by you guys before I went. Here are my thoughts as to why pH is not dropping: 1] Improperly calibrated pH controller; 2] Improperly adjusted CO2 flow rate from regulator; 3] Excessive flow from Sedra 9000 (may need to throttle with ball valve); 4] Possible air bleed into CO2 line running to Sedra pump.

I calibrated the controller, set the CO2 bubble rate, and connected the CO2 line to the pump myself and am reasonably sure they have no issues but I will double-check when I go to the client site. I am currently leaning toward excessive flow as a possible cause of the problems because I can't come up with any better reasons. If you've got any advice I would greatly appreciate it. Thanks!
 

tedr108

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Is the sump sealed? If it is an open-top sump, that is probably where you are losing your CO2.

With such a powerful pump, it would not surprise me if air is being sucked into the CO2 line. This happened to me on a much weaker pump. The simple test for that is: When the CO2 is off, do you still get air bubbles coming out of the pump outlet in the tank. If so, you are bringing in air. I'm not sure, however, that this would cause a reduction in CO2 ppm. It is not likely that you are losing CO2 thru your CO2 line.

What is the CO2 bubble rate you have set now?

Personally, I would use a pH test kit (rather than a pH controller) until you get everything stabilized. Unless you purchased an expensive pH controller, they can have issues.
 

tinkerman

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Dec 8, 2007
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I have a 125 gal tank and have a rena xp4, 300 gph power head , and 300 gph pump( running exteral co2 reacter) no issues with co2. I would agree with the sump idea for co2 loss if thier running one.
 

travis

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I added a ball valve to the return line and used it to throttle the pump slightly. CO2 levels increased within minutes. Problem solved - for a number of reasons I suspect. Throttling the flow caused a finer mist to be delivered into the system because of better back-pressure on the pump/needle-wheel. It also reduced turbulence through the overflows and sump because flow-rate slowed, thus decreasing the rate of CO2 outgassing.

Thanks for all of the advice guys!
 

Tom Barr

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Address the sump issue if you can also, over flow section and the bubbles, seal it up etc down below.

Needle wheels are based on dwell time, the longer the dwell time, the more the bubble gets whacked to bits.


Regards,
Tom Barr
 

rusticitas

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May 4, 2006
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Related, but side question...

What commercially made sumps are available that are sealed as you recommend for use with CO2? I am initially just curious to see what the they look like in comparison to other commercial sumps.

Or, does someone have photos of one with the plumbing in and out? I am trying to diagram a system for myself, never having used/had one before and want to verify that what I think I understand the system to be, that I am accurate...
 
M

mrkookm

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I use a faily descent size sump which is not sealed, has multiple points where I have co2 loss and I'm still able to maintain correct PPM range with ease. While I'm sure co2 efficiency will increase if the sump is sealed, it's not necessary if your injection method is good.
 
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mrkookm

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used a 1100gph @ 28ft head pump for a while but now upgraded to a bigger pump because I'll be adding in some in-line canisters. My Mazzei is plumbed inline via a loop and I adjust to send around 500~550gph towards Mazzei.