Advice on a ph controller

Discussion in 'Carbon Dioxide (CO2)' started by willson, 29 Jan 2008.

  1. willson

    willson Member

    Messages:
    31
    Hi, I came home to find my co2 bottle had managed to creep upto 3bar instead of the usual 1bar :rolleyes: . Its the second time its happened in a few weeks. All the fish at the top, luckly didn't loose any fish this time, but they obviously werent happy.

    So in light of this it would seem a good idea to get a basic controller. Can anyone recommend a budget one? Would something like this be suitable?

    Thanks :)
     
  2. zig

    zig Member

    Messages:
    686
    Location:
    Dublin Ireland
    Sounds like your needle valve is duff :? or your having extremes of temperature in the room.
     
  3. Themuleous

    Themuleous Member

    Messages:
    4,126
    Location:
    Aston, Oxfordshire
    Yeh this sounds like a problem with the reg. Is it JBL?

    pH controls are expensive, even the 'cheap' ones. Personally I've never seen the point of them. I never change the bubble rate on either of my two CO2 kits just run them 24/7. A pH controller to me seems like a over-complication of a simple system and just another thing that can go wrong.

    If it were me I'd try and find out why the reg was causing the pressure to go up before I tried to fit the result :) the cylinder isn't getting hot during the day is it?

    Sam
     
  4. willson

    willson Member

    Messages:
    31
    There was a link to acheap one hiddenen in my first post. Ive changed the reg now :)

    But still intersted in a ph controller. The bottle isn't exposed to any heat change as such.

    Thanks
     
  5. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,937
    Location:
    Chicago, USA
    Hi,
    In my opinion, while PH controllers may seem like a good investment, in reality they can sometimes cause more trouble than they are worth.

    The first problem is that the probe can only measure the pH of the tank water. It is a fundamentally flawed idea to correlate tank water pH with CO2 concentration. The reason for this is due to the fact that there are many acids in the tank water other than Carbonic acid formed by CO2. For example if you dose Potassium Phosphate (which you should be doing) the phosphates form phosphoric acid. There can also be tannic acids released by wood, and a host of other types of organic acids. If you measure the pH of your tank water right now and use that value to calculate the CO2 concentration it is a guarantee that the value will be artificially high.

    The second problem is in the way that the pH is regulated. In the beginning there will be a large injection to bring the pH to within the set point, then the controller will shut down or slow the injection rate. As the pH rises and falls above or below the set point the controller will respond to the fluctuations by raising or lowering the injection rate. The result of this action is that the CO2 concentration is rarely ever stable. Fluctuating CO2 concentration brings the onset of some types of algae.

    Plants produce a type of enzyme which responds to the CO2 concentration level in the environment. This enzyme, acting as a sensor allows the plant to regulate all of it's other functions (such as photosynthesis, growth, food production and nutrient uptake) based on the concentration level. If the level is stable then these other functions are also stable, but unstable CO2 levels has a devastating effect on the plant metabolism. A pH controller therefore contributes to unstable CO2 levels by the mere fact that it continually varies the injection rate. It is much better to have a stable injection rate set to a high enough level to satisfy the plant demands throughout the day while minimizing the fluctuations. The pH of an aquarium has been given too much priority in relation to the other tank parameters. Plants simply don't care about the tanks pH as much as they do about nutrient availability and CO2 concentration levels.

    Cheers,
     
  6. JamesC

    JamesC Member

    Messages:
    1,276
    Location:
    Bexley, Kent
    Agree totally with ceg. pH controllers just cause too many problems. Another one is that they do need calibrating as they tend to drift a bit over time, more so the older they get. It only takes a small variation to change CO2 levels quite a bit. Everytime recalibration is done the CO2 level is also going to change.

    The only thing that I think they can be good for is as a safty device. Control CO2 using bubble rate and set pH controller to a bit lower than the tank's pH. This will provide you with a constant CO2 rate but in the event of a regulator fault or tank dump the CO2 will be cut off.

    James
     
  7. Dave Spencer

    Dave Spencer Member

    Messages:
    1,389
    Location:
    N. Wales
    Matt (i think?),

    Have a read of Clive`s article in the Cookbook section of this forum, which is about CO2 measurement using a drop checker.

    I have given Jim some 4dKH solution, so once you get the glassware, you are on your way for a far cheaper way of controlling/measuring CO2 levels.

    Dave.
     
  8. sks

    sks Guest

    wilson,

    If you want a pH controller I can sell you my Dennerle one. I have an old aqua medic one before they implemented the cushioning band that I could sell to you too (use at your discretion!!).

    In all my years of playing around with regulators I've never over shoot it as badly as you have. I'm currently using the needle valve of a cheap D+D regulator attached to my Dennerle profi via solenoid. The aqua medic regulator is also very good. I didn't know that the JBL needle valves were that coarse.

    It's nice not to HAVE to use pH controllers, it makes the tank look that much neater. :D
     
  9. willson

    willson Member

    Messages:
    31
    Im currently only using a bubble counter and a drop checker. The sera bottle is just a reg with a gauge. Maybe I should fit a needle v/v before the solenoid?.
    I was pretty shocked to see it overshoot so much :(
     
  10. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,937
    Location:
    Chicago, USA
    willson, I'm confused. Are you using one of the Sera CO2 kits like the one shown here? http://www.sera.de/index.php?id=408&L=1Perhaps if you could post some pictures of your rig we could have a clearer idea.

    If so the regulator attached to the bottle is controlled by the knurled round knob which is attached to a needle valve. As Sam pointed out earlier there could be a problem with this regulator or as the bottle empties sometimes there is a surge in pressure.

    Cheers,
     
  11. willson

    willson Member

    Messages:
    31
    Yes i am sorry didnt realise that was the needle v/v cheers.
     
  12. SuperColey1

    SuperColey1 Member

    Messages:
    2,668
    Location:
    Lincoln UK
    sounds like the cylinder was emptying to me. Big problem with single gauges regulators as you can't tell when the cylinder pressure is dropping.

    On another note I know with mine that if I adjust the cylinder outflow then the needle valve does let more or less amount through without adjusting it, although I assume it will max out at some level?

    Fingers crossed.

    Andy
     

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