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Surface skimming and CO2

Discussion in 'CO2 Enrichment' started by RlxdN10sity, Feb 8, 2007.

  1. RlxdN10sity

    RlxdN10sity Prolific Poster

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    I've read more than once that surface agitation is a detriment to CO2 levels in the tank. I notice if I do not run the skimmer I get a bit of a film built up on the surface and it seems my angel fish is more inclined to go to the top and gulp as if needing air. Am I killing my CO2 levels by skimming? Is it not recommended?
     
  2. VaughnH

    VaughnH Lifetime Charter Member
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    I don't see how skimming affects the rate at which CO2 leaves the water, as long as the skimming doesn't ripple the surface excessively. My constant water change system skims my surface constantly, and I have no trouble getting to 30-40 ppm of CO2 in the water. I do think I run a higher than usual bubble rate doing so though. If I had DIY CO2 that might be a problem.
     
  3. Tom Barr

    Tom Barr Founder
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    Actually...... it's highly recommend.
    By most anyone that does a lot of tanks. ADA uses them on larger tanks, his giant tank has them.

    I have them.

    CO2 is easy to add, you just add a bit more than without surface movement.
    The real benefit is the exchange of O2 and better mixing.

    I like lots of current and mixing, it's good for plants and reduces algae. There's a lot of evidence of that both in FW and marine systems.

    It helps exchange nutrients as well as CO2.

    In most cases, like yourself, folks reduce their surface movement and flow down too low. Their fish gasp.
    Many blame the CO2.

    It's mostly the low O2.

    If the plants are growing well, that can off set that*(but only during the day, earyl am, they gasp), if you have few fish, that also can off set that.

    If you have good surface movement, etc, then you lose some CO2, so what, it's cheap and you just turn the needle valve a 1/16" of a turn etc.

    That way there is plenty of O2 and CO2 and the tank is well mixed, the CO2 is not allowed to build up as much this way and the O2 is not allowed to get too low.

    So it's a mix of 3 things really, not enough plant growth/low O2(both plant growth and surface exchange) and too much CO2.

    I've found it easier to maintain a stable level of CO2 ina high flow tank, less fish issues and better long term results.

    Some folks enjoy suggesting surface movement is bad.
    That's rubbish.

    You can go over board and make it a torrent, but some slight rippling is fine.
    Or if the degassing exceeds the CO2 diffusion system's capacity (that is often what happens and folks complain they cannot get enough CO2 into their tank etc)

    When you use a skimmer and over box, and a wet dry etc, you should raise the level in the weir box to about 2-4" drop only.
    No more.

    The wet/dry bioball tower needs duct taped up so no air exchages in there.
    That solves about 95% of any issue.

    Regards,
    Tom Barr
     
  4. RlxdN10sity

    RlxdN10sity Prolific Poster

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    Good to hear, or read that is. I've been skimming for over a year but I do it with a canister filter so there is no open sump box to worry with. I also felt it was much better to skim so that I would be constantly exposing water to atmosphere to absorb O2 as needed and eliminate any worries with the fish. Everyone keeps telling me that the most likely problem I have with growth is low carbon so I'm trying to increase levels by adding more and/or decreasing loss. My Red Sea drop check should be arriving today so I'll be mixing KH solution and getting that setup tonight and finally have an accurate reference for CO2 levels in the tank. I've noticed links to several threads on preparing KH solution and setting up the drop check to measure CO2. Would someone be kind enough to point me toward the thread that is most recommended. Thanks...
     
  5. Tom Barr

    Tom Barr Founder
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    I'm goading Vaughn into a nice article like synopsis:D

    That way we can arrive at some consensus about what to do.

    Two vendors on both sides of the pond will sell the KH reference solution diluted down etc perhaps.

    Using Bromothymol blue is the best alternative and the vendors should be able to get this in large amoutns as well as small 1 oz sizing as well.

    You add 3 drops to 6mls of KH reference solution basically.

    Regards,
    Tom Barr
     
  6. RlxdN10sity

    RlxdN10sity Prolific Poster

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    But how do I prepare a KH reference solution correctly? Will the Red Sea unit come with Bromothymol? If it does not come with it should I order some seperately or can I use whatever it comes with? Thanks...
     
  7. VaughnH

    VaughnH Lifetime Charter Member
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    As far as I know all pH test kits that measure pH from about 6 to about 7.2 use bromothymol blue, so you can just use your pH test kit reagent.

    Mix 6 grams of bicarbonate of soda (baking soda) into 1 liter of distilled or DI water, giving you 200 dKH water. Then take 10 ml of that and mix it with 490 ml of distilled or DI water to get 4 dKH water. Add enough of this water to the Red Seas CO2 Indicator to fill it to where they say it should be filled, and add 2 or 3 drops of pH reagent to that, to get a good, easy to see blue color. The amount of the reagent you use isn't critical at all.
     
  8. RlxdN10sity

    RlxdN10sity Prolific Poster

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    Vaughn, thank you so much for that simplistic explanation. I was trying to read this thread - Making Standard KH solutions - http://www.barrreport.com/articles/2630-making-standard-kh-solutions.html - and nearly went insane. Do you happen to know of a lab supply where I can purchase KH standard that is cerified like Tom mentioned? I will make it the way you have instructed until I can source a supply, but a certified standard would eliminate any mistakes I may make from the equation.
     
  9. VaughnH

    VaughnH Lifetime Charter Member
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    Don't worry about mistakes right now. Use your KH test kit to see if the batch of 4 KH water is close to being that per the kit. If you are off even 20% it is still better than what you have now.

    If you don't have a scale capable of measuring 6 grams accurately, you can mix a little baking soda into a liter or so of distilled water, check the KH of that with the test kit, and if it is very high, dilute some of that water about 4 to 1 with more distilled water and repeat the KH test. Once you get a KH that you can measure, you can dilute directly to 4 dKH using the dilution equation Tom provided. It will only be as accurate as yout test kit, but still that is better than any other method you now have. In a few weeks we should be able to buy the water already mixed and done accurately.
     
  10. Tom Barr

    Tom Barr Founder
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    Yes, the 4 KH solution in 500mls amounts will be sold for about 8.99$. Should last several years. The pH indicator will run about the same and also last several years.

    Regards,
    Tom Barr
     
  11. jeff5614

    jeff5614 Prolific Poster

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    Good to hear! Who will it be available from?
     
  12. Tom Barr

    Tom Barr Founder
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    Greg Watson's company and AE in the UK.

    Regards,
    Tom Barr
     
  13. kaaikop

    kaaikop Junior Poster

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    Hello to all, I am new to this forum... which I find very interesting.
    I have been pondering with the idea of "skimming" for a while, makes sense to me,
    however most planted tank folks would recommend against it...
    This is the first place I see where it is actually encouraged... kind of goes in line with what I was thinking.
    Would somebody point me to a good skimming unit? doesnt have to be something that is hooked with filter outlet...
    I wouldnt mind buying an extra device (HOB type), that would increase the surface agitation (like some of the protein skimmers for SW tanks).

    Thanks!

    Forgot to mention: the tank is 150G
     
  14. Tom Barr

    Tom Barr Founder
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    I would never tell anyone to avoid surface skimming.
    That's bad advice.

    Why?
    Let us be practical for a moment.
    Light= better light use with SS
    Films, less with SS
    Better filtration, hides tubing with SS

    Why not? Supposedly some claim it removes CO2. If you raise the level inside the over flow, then it does not remove much to ever be an issue, anyways, why is it an issue?

    I can easily add a tad more CO2.
    If you are sat the limit of CO2 addition, then you have something wrong with the CO2 system(inefficient/not enough flow through/ undersized for the tank etc) not the surface skimmer.

    The other safety thing is that the levels of O2 will not drop as much with SS and Wet'drys etc if something goes sour with plant growth or with low plant biomass.
    I can bring any plant back that's taken a beating, I cannot bring fish back to life.

    Just for clarification:
    The HOB skimmers we are talking about are not protein skimmers, they are overflow box surface layer skimmers.

    CPR and various other brands are all good, the less amount inside the tank, the better.

    I always add a piece of 1/2 cork bark etc to my skimmer boxes to hide the things, then add plants like Java fern etc to the cork using U shaped wire nails/staples.

    You cannot even tell what the overflow is after I get done with it.
    As far as heavier particulate materials, a large weekly water change removes all that.

    You will lose a little CO2, but it's not anything to fret over, it's easy to add more CO2 and cost very little.

    I had a 90 gallon tank with DIY CO2 yeast, and a wet dry(unsealed) and used 4 x 2liter bottles changed every other week without issue with very high lighting.

    So it can be done effectively even with weak CO2 sources.
    But it's much wiser to have a CO2 gas tank system with larger than 40-50 gallon tanks.

    You might lose 5-10% CO2 at most, but given the cost of CO2, using it 10 hours a day, and 5-10% loss factor relative to cost, say 15$ for 10lbs of gas, that means you will spend about 1.50$ more per year or to 6months so in added CO2 gas cost.

    Oh my wallet hurts:p
    If you gassed your fish or have lower DO levels or loss light levels will add up to more $$ faster I'd suggest.


    Regards,
    Tom Barr
     
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