How to balance off O2 vs CO2?

Discussion in 'Carbon Dioxide (CO2)' started by nickmcmechan, 23 Mar 2008.

  1. nickmcmechan

    nickmcmechan Member

    Messages:
    224
    Location:
    Dalkeith, Scotland
    Hi,

    I have a 180l SA setup which I've ordered a pressurised CO2 kit for.

    I run the tank at 32 degress C, which of course lowers dissolved O2, therefore I run air into the tank via the outlet of the powerhead. This causes a lot of surface agitation.

    I experimented with turning of the air pump yesyerday and woke this morning to find all the fish hanging at the surface. Immediately I put the air pump back on and the difference was instant.

    So, how do I run an air pump into the tank as well as CO2 injection without gassing off too much of my CO2?
     
  2. Ed Seeley

    Ed Seeley Member

    Messages:
    3,262
    Location:
    Nottingham
    Hi Nick,
    I've moved this into the CO2 forum as I thought it was better there.

    As to your question. The levels of CO2 and O2 dissolved in the water are independant of each other. High CO2 does not mean low O2 and vice versa. You can have high levels of both, or low levels of both. If you're fish are struggling to breathe overnight then I feel you may need to look at the stocking levels and conditions in your tank I'm afraid. What's the stocking?

    Are you keeping discus and if so is this why your temperature is so high? Please note that it only ever reaches those kind of temperatures for the very height of the dry season in the wild for discus. Keeping fish at higher temperatures speeds up their metabolism and is not natural. As to it preventing disease as many discus keepers say, maybe the tank bred strains are that weak to need help, but most disease organisms will adapt to these temperatures! I use high temperatures to help sick fish (it's especially good at killing white spot), but then acclimatise them back to normal temperatures (about 27oC for breeding SA dwarfs) and they thrive.

    I'd drop the temperatures to less than 30oC at least and you will find the O2 shortage becomes less of a problem!
     
  3. Themuleous

    Themuleous Member

    Messages:
    4,126
    Location:
    Aston, Oxfordshire
    I'll also add that if your plants are growing nicely they will produce a lot of O2 for the fish. You might want to consider a solenoid to turn the CO2 off a night.

    Sam
     
  4. nickmcmechan

    nickmcmechan Member

    Messages:
    224
    Location:
    Dalkeith, Scotland
    thanks guys,

    its not discus i have but rams and festivums, shoud i drop the temp to 28?

    maybe i shoud run a ower output air pump too??
     
  5. Ed Seeley

    Ed Seeley Member

    Messages:
    3,262
    Location:
    Nottingham
    For Rams and Mesonauta you should be able to run it lower than that, but I'd start by slowly dropping the temperature to 28oC, but do it by a degree a day for 4 days so it's as slow as possible - not always necessary, but it's better to do things slowly in a tank and then you can monitor the changes.

    Onve you've lowered the temperature the Oxygen carrying capacity of the water will go up and an air pump shouldn't be needed. What are the tank specs? i.e. numbers and types of fish, planting, fertilising, filtration etc. My 180l tank hasn't got any air pumped in, in fact none of my tanks do and the fish are never gasping at the surface.
     
  6. nickmcmechan

    nickmcmechan Member

    Messages:
    224
    Location:
    Dalkeith, Scotland
    your probably going to flame me!!!! lol

    my guilty secret is that i overstock, i have 4 angels, 4 festivums, 5 rams and a couplr of pictus in there..i know i know!!!

    right now i'm doing a 1/3 ei dosing with double excel...when i get the presurrised co2 i'll switch to full ei dosing.

    theres about 30 swords in the tank, not looking that great, but only had about 1/2 of them for 8 weeks, kinda wondering if they are re-generating new leaves just now and old ones are going...want to push the process on with pressurised

    filtration is two external cannisters along with the internal that comes with the juwel rio 180, peat granules in two of the filters

    thanks
     
  7. Ed Seeley

    Ed Seeley Member

    Messages:
    3,262
    Location:
    Nottingham
    No flaming here, my oldest tank is overstocked too. I've got 40 odd Cardinal tetras, and a fair few other fish in there too. We all do it sooner or later. I might be tempted to look at whether you could rehouse some fish though. The Mesonauta get pretty big when mature and would really be best in a bigger tank.

    However I'm surprised you're having such critical oxygen problems with such a high turnover. What are the two canisters? How are you returning the water? If you've got either spray bars or open returns setting them so that there is a good ripple on the surface should ensure good gaseous exchange. Do you have all the filter returns set very low to reduce loss of CO2? This is a bit of a myth and you're best having decent exchange at the water's surface.

    You don't mention the water changes, but if you're going to use EI you really ought to be doing large water changes now to get the organics down low. With high stocking you're going to really have to make sure you stay on top of this and may even need to do more water changes than normal EI. For now go with 50% a week, but at the first sign of algae or any other issues you may need to do this twice weekly - you can't change too much water IMO.

    With 30 swords, unless they're all dwarf chain swords or the more compact hybrids, you're going to have a very full tank! It could look great though, my overstocked tank is full of too many biggish swords and I love the chaotic look it has!
     
  8. nickmcmechan

    nickmcmechan Member

    Messages:
    224
    Location:
    Dalkeith, Scotland
    yes, i've deliberately set the canister outputs so that ripple is minimised to maintain co2 levels

    the festivums and angels are small just now, ideally i'd like them to each have their own tanks in the future

    not sure how the mid week water change affects the ei dosing, but wondering if its ok anyway as in reality my weekly water change is more like 60-70% (on all my tanks - yes i overstock them all! - i'm a bad man)

    i'm really not sure which swords they are, but the height is never above 6" and i'd really like them to grow tall, assuming they are true swords...maybe see a diff when the pressurised setup comes

    thanks again for the gr8 advice
     
  9. Ed Seeley

    Ed Seeley Member

    Messages:
    3,262
    Location:
    Nottingham
    No worries on the help. Lift the filter outputs to just under the surface so the surface is rippled and don't worry about the mid-week changes at the moment. If they're only babies then I don't think you're really overstocked, yet...

    Once you've raised the outlets and lowered the temperature you should be able to turn the air pump off without any problems and, once you get it, add pressurised CO2 without problems.
     

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