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Co2 And Kh?

Discussion in 'Planted Chit Chat' started by sjdriscoll, Nov 15, 2007.

  1. sjdriscoll

    sjdriscoll Member

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    I have just planted up my 20gal and want to raise the CO2 levels from 14ppm to ~ 25ppm to help the plants.

    Trouble is that my parameters are as follows;

    pH 6.8 kH 3'd

    When I look on a pH/kH chart at my CO2 it is 14ppm. Do I need to raise my kH in order to achieve a higher CO2 level?

    I currently have a small tetra CO2 aerosol unit with a membrane diffuser but have now made a DIY CO2 unit. Could I just run this and see what happens to my levels? I am worried about a pH crash as my kH is pretty low.

    I use RO water with RO Right 20% once a week.

    Cheers for any help
     

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  2. nry

    nry Member

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    From experience I found the Tetra Optimat thing useless. I have no concept how on earth you can maintain stable CO2 with it, let alone regulate what level this is.

    The DIY kit should be better, you can alter the amount of sugar/yeast to get 30ppm, and using two bottles of mix (swap one Wed one Sun to keep output stable) is a good idea too.
     
  3. sjdriscoll

    sjdriscoll Member

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    Thanks for the help. The DIY should run for 2-3 weeks I think?

    Will I need to up my kH to buffer my pH?
     
  4. Underwurlde

    Underwurlde Always look on the bright side of life..

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    Bank on DIY kit mixes lasting for about a week, but dep on size really.

    I would buffer your water more! Use Bicarb I think.

    Why do you use RO water?

    Andy

    PS. don't rely on pH / KH LUTs for CO2 ppm. The formula holds true (i.e the table is correct) BUT measuring KH is fully of errors and because of this, pH / KH LUTs aren't so accurate. Better use in-tank dropper checkers.
     
  5. sjdriscoll

    sjdriscoll Member

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    Cheers - only a week huh? Ok then.

    I use RO because the level of phosphates in tap water down here is off the scale. I had a lot of algae problems using dechlorinated tap water so switched to RO. The fish seem to prefer it to my tap water too.
     
  6. Themuleous

    Themuleous Member

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    DIY yeast mixes should be changed each week to maintain the stable CO2 level in the tank. Run two on a 20g tank to give you enough CO2 production.

    Re the KH, a KH of 3, is fine, my tank runs at kh1 no problems. BTW why not use RO cut with tap water? I used to use ro right but its dam expensive and it never was very accurate. My tap water is gh17, kh15, PO4 5ppm and NO3 40ppm, if memory serves so I know what you mean about high PO4 and the rest however all other things are important, why pay to add them?

    Sam
     
  7. sjdriscoll

    sjdriscoll Member

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    Thanks Sam.

    Good point - well made.

    So I could cut my RO with a % of the waste water to achieve the same result - what % do you reckon?

    As per the C02 - if my kH and pH stay the same how can I up my C02 ppm? Is it just a case of pumping in more C02 and than this will change the other parameters?

    Cheers
     
  8. Underwurlde

    Underwurlde Always look on the bright side of life..

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    Yes. (For the record, you cannot 'make' CO2 by fiddling with pH and KH).
     
  9. Themuleous

    Themuleous Member

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    Yeh, unfortunately the only way to increase CO2 is to add more. In the co2/ph/kh relationship, its always the pH that ends up changing. I.e. increase co2 or lower kh and the ph goes down, decrease co2 or increase kh and the ph goes up. To add more co22 either yet a second kit or switch to pressurised, which IMHO is much easier.

    Do you know the gh/kh of your water at present? I work on the basis of around 15lt ro with 5lt tap, that gives me a gh of around 4/5 with my tap water.

    Sam
     
  10. sjdriscoll

    sjdriscoll Member

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    Thanks for the info. My GH is 7d and my kH is 3d - i'm looking to increase the kH to 4 but its proving surprisingly difficult! I added more RO Right as per instructions but the kH remained the same! I didn't risk adding any more but will try to build it up at every water change. I'll try your ratio and see if that helps. I'm in Devon and the water is very soft!
     
  11. Themuleous

    Themuleous Member

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    BTW I used to run a tank with well over 5ppm PO4 in it, no problems re algae. Seems odd to me to use RO water in a soft water area, esp when you're just using an additive to get it back to tap water softness. If you're worried about PO4 could you not use a PO4 removing resin in the tank?

    If I were you, I'd live with the high PO4 and save myself a load of money by using the water straight from the tap. What I would give to have soft water coming out of my tap!!! :lol:

    FYI I know someone else who has 10ppm PO4 in the tank, no algae issues either :)

    Sam
     
  12. xxBarneyxx

    xxBarneyxx Member

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    Yeah I would just use some phosphate remover in the filter or prefilter the water through a phostphate remover first. If the tank is heavily planted then phosphate shouldnt be a big issue anyway as the plants will use most (if not all) of it.
     
  13. sjdriscoll

    sjdriscoll Member

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    Yes, I can see your points. Lots of people down here ( at least the ones I talk to) seem to use RO. I got the unit on this advise and it did clear up my algae so I'm a happy chappy. My tank wasn't heavily planted then as it is now so maybe I could start to use tap again. I only use 20litres a week for water changes and the waste RO water is used on my garden etc.

    I may look at a phosphate remover in my filter. Any favourites? Tip?

    Thanks again.
     
  14. Themuleous

    Themuleous Member

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    Its your call ;)

    I hear rowa-phos is good, but Ive never used then, no need IMHO! :lol:

    Sam
     

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