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Thread: Need advice on which step to take next re improving my co2 dissolution on my big tank

  1. #1

    Default Need advice on which step to take next re improving my co2 dissolution on my big tank

    So, I've been reading a lot lately, here and over on Barr Report about the various methods of co2 dissolution. Most of it I've read before, just refreshing my memory. The system I have at the moment is not working. I currently have a Cerges style water filter reactor (see photo). It is tee'd off from the main return line, with a ball valve inline so I can adjust the flow through the reactor. To be honest, I haven't found this setup to be earth shatteringly effective. Lots of people use them and lots of people rave about them, but I am finding that above 2 bubbles per second, the gas builds up inside the reactor. If I increase the flow, whole bubbles are being forced out of the reactor. My tank is about 1400L, with another 150 or so liters in the sump underneath. At the moment I cannot even get close to turning my drop checker green, at any point during the day...



    At this point I am considering 3 different alternatives:
    1) Build a larger reactor. After petetheplantkillers suggestions I am thinking 150mm pipe and about 1.2m tall, with 40mm pvc in and out - this one would have all the flow from the return pump going through it, then flow directly into the tank. (roughly 7000L per hour) The downside is that being pvc, I can't see whats going on inside, which is something I've relied upon so far. Also it is going to be a reasonably expensive piece of junk if it doesn't work for whatever reason.

    2) Try feeding my existing setup with a dedicated needle wheel pump rather than coming off the return line (I have a couple just sitting there from when I was planning a marine tank) to mechanically break up the bubbles before they enter the reactor. I've also read about a few people reversing the flow through the reactor with good results. Advantages - cheaper, quicker easier and still a potentially viable solution.

    3) A mixture of the two - buy a longer 20" water filter housing (these are relatively expensive unless I import from the US) and implement all the steps mentioned in 2). Advantages - again it would be a transparent housing, allowing me to see whats going on inside, hopefully with the taller depth inside the filter, I could run a higher velocity of water through without the bubbles being pushed out, resulting in more turbulence and more dissolution?

    Love to hear your thoughts...

  2. #2
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    Try a smaller diameter pipe inside the reactor. Similar size to the plumbing feeding it. Will allow for more space for things to flow around giving it a better chance to dissolve.

    Tim

  3. #3

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    Hi Mundi,
    Yesterday I followed your suggestion. Instead of installing a smaller pipe, I went with a custom clear bodied filter cartridge, designed to house special calcium scale removing crystals. I emptied out the crystals, reversed the flow by flipping the unit around on its mounting, and voila. I was running 2.5 bubbles per second, however this was not enough to turn the drop checker green. I have upped to approx 3.5 bubbles, so I'm going to monitor things over the next day or so and re-evaluate. If it works I'll be very happy! I will try to get a couple of photos of the new setup when I get a chance...

  4. #4
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    Unless these said bubbles are the size of a small child's head, I would say that you would probably need 15 bubbles per second plus two reactors to get this monster saturated with CO2....

    Great work to get things improved though.

    Will be following this one.

  5. #5

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    Holy crap... That's a lot of CO2! For now I guess I'll just up the bubble rate until the reactor can't handle it any more and see where that gets me... Sounds like

  6. #6
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    Quote Originally Posted by Kris View Post
    Holy crap... That's a lot of CO2! For now I guess I'll just up the bubble rate until the reactor can't handle it any more and see where that gets me... Sounds like
    Agree. I wouldn't just believe your drop checker. Check pH drop with a pen if possible and watch the plants. This tank is very deep and large so alot of diligence will be required.

    not to diss this forum but I think you need to also ask UKAPS too.

    I know that Tom Barr had a similar high tech setup with O2 injection etc. I know Amano used some sort of pressure system to pump CO2 into the Lisbon aquariums.

  7. #7
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    A PH controller will help also. With large tanks they make life easier as the fluctuation isn't as high. Easier to keep it near a targeted range rather than bringing up up from 0ppm to 30ppm CO2 level. Set the bubble rate at the maximum the diffuser will handle and let the controller turn it on and off at the desired level. Google aquarium CO2 level chart and it will show the corelation between PH, KH and CO2 parts per million. About 30ppm is good.

    Tim

  8. #8

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    Success! Well sort of...

    I have a green drop checker, although the drop checker is leaking gradually in that the volume of liquid inside the checker is increasing, so obviously some tank water has found its way inside somehow...

    However I am seeing other positive growth signs. The aponogetons which have been more or less dormant for months have suddenly started growing full sized leaves again:


    The recent growth on the sunset hygro is looking healthy:


    And even the java fern is sending out new growth:


    Not much pearling going on yet though. Now I am starting to wonder whether I would be better off plumbing the outlet from the reactor directly into the tank rather than back to the sump. My reasoning is that going back to the sump, it is mixing with freshly oxygenated water which has cascaded through over the glass divider into the chamber with the return pump (I can see little bubbles of air being pushed under the surface by the arriving water coming over the glass). This leads me to believe that there is a bit of gassing off happening in this chamber, before the water makes its way back to the tank. By running the return direct to the tank I can eliminate this, but it will mean another check valve, and another pipe going in the tank. Not sure if the benefit is worth the effort?

  9. #9
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    I agree reactor straight into tank would be more efficient. Why can't you put the reactor on the existing pipe that pumps into the tank?

  10. #10

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    Because the reactor is too small for the size of the pump and its output. It's currently running at about 6 or 7,000L/hour, using 40mm plumbing. The reactor has 20mm inlet and outlet, and the flow would blow the bubbles straight through undissolved... That was how the tank was originally setup and the co2 dissolution was terrible.

  11. #11
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    Sorry - I did know that but thought you could install a small parallel loop with a bypass for the bulk of the flow. If you already have it working in the sump then perhaps that is the cleanest option. Can you route the outflow from the reactor so that it enters the sump nearer the pump pickup and avoid the cascade over the divider?

  12. #12

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    Its reasonably close now, and what I've found is that if its too close, the induction from the pump sucks water through the reactor and increases the flow through to an undesirable level. I guess I could shut the ball valve further to compensate though...

  13. #13
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    Any luck with improving your design?

  14. #14

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    Yeah - I posted about it in the main tank thread. I ended up running two of the filters In line, so that any bubbles escaping the first would get caught up in the second. I never did figure out how to feed it from the main return pump so I have a small 8 watt power head feeding the co2 loop and the return tees back into the main pump return from the sump. This setup is pretty effective and can disolve a lot of co2. Love that it is transparent too so you can see exactly what's going on with the flow and bubble dissolution etc...

  15. #15
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    Good to hear,
    Where did you get your clear filters from, im looking at getting something up and going in my 6x2x2 the current ista external is just not cutting it :-)

    Quote Originally Posted by Kris View Post
    Yeah - I posted about it in the main tank thread. I ended up running two of the filters In line, so that any bubbles escaping the first would get caught up in the second. I never did figure out how to feed it from the main return pump so I have a small 8 watt power head feeding the co2 loop and the return tees back into the main pump return from the sump. This setup is pretty effective and can disolve a lot of co2. Love that it is transparent too so you can see exactly what's going on with the flow and bubble dissolution etc...

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