Ph of tap water in Cape Town

Discussion in 'Advanced Topics' started by hartz, Mar 28, 2009.

  1. hartz

    hartz

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    Lately (for about four months now, I think) my tap water has got a very low PH. Before I started filtering with Peat, I had to use PH-Down. Now I'm scared of changing the water - the past four months things seems to have gotten quite bad!

    1. Am I alone in this experience, and
    2. What can I do about it? My Tank Ph is already low and stressing my fish.
     
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  3. Henk Hugo

    Henk Hugo

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    Hi Hartz,

    I have moved yout thread into the section where Prof B posts. He can explain things MUCH better than what i can :D
     
  4. Rowland

    Rowland

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    Where exactly are you situated Hartz?
     
  5. OP
    hartz

    hartz

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    In the Stellenberg area (near Stellenberg High School). I think our water comes from the reservoir at De Bron road.

    Speaking of area, I may be moving to a house closer to Cape Gate soon - that is on the other side of the De Bron hill, but probably still gets its water from the same reservoir.
     
  6. brentnorm

    brentnorm

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    Would you like to bring me a water sample and I will test your PH for you. I am in Sonstraal.
     
  7. OP
    hartz

    hartz

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    Thank you, I'd like to take you up on this offer - You (will) have PM (soon)
     
  8. brentnorm

    brentnorm

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    No problem. Just let me know.
     
  9. TyroneGenade

    TyroneGenade Mad Scientist

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    How low is your pH? What is the pH of the tap water?

    Go to a health food shop/pharmacist and get some calcium hydroxide. You won't need much... Dissolve a little into a beaker of water and add it SLOWLY to the tank till you reach the desired pH. This should help buffer the pH but really, unless the pH is below 3, I wouldn't worry about it. Changes in pH and fiddling with water chemistry causes more damage to the fish than the actual pH.

    How do you know the pH is stressing the fish? What are they doing? The major trouble with a low pH is that it will dissolve metals which can be toxic.

    DO NOT go to a LFS and ask them for a chemical to raise the pH. They will normally give sodium bicarbonate which would work well if you have hard water but is useless for long term pH stabilization in fish tanks filled with soft (Cape Town) water. Eventually you will pickle your fish in salt. I recomment Ca(OH)2 because it will harden the water and establish a Calcium Carbonate buffer in the tank.

    Remember:
    CO2 + H2O <=> H2CO3 <=> H+ + HCO3- (CO2 acidifying the fish tank)
    Ca(OH)2 + 2H+ + 2HCO3- <=> Ca(HCO3)2 + 2H2O <=> CaCO3 + 3H2O + CO2

    With the Ca2+ in solution any CO2 dissolving into the system will replenish the buffering system. Only as much Ca2+ will dissolve as is needed to buffer the pH so you won't have to worry about the Ca2+ hardening the water too much.

    You can, alternatively, mix some shell grit or oyster shell into the substrate or filter medium but this isn't always effective as the shell grit can develop an insoluable film. The Ca(OH)2 will quickly dissolve.

    Becareful! The Ca(OH)2 is very caustic and can burn you.
     
  10. brentnorm

    brentnorm

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    Also try one of those PH Alerts from Seachem to put in your tank, it's constant PH monitering.
     
  11. Dirk

    Dirk Dwarf Catfish

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    What Tyrone has explained here is perfectly correct. (Tyrone is doing a doctorate in Biochemistry on aging in Nothobranchius killifish and is therefore a highly qualified scientist in this field).

    Instead of the somewhat caustic Ca(OH)2 I could also suggest that you can add a mixture of Sodium carbonate (Na2CO3) (or Calcium carbonate (CaCO3)) and Sodium bicarbonate in a ratio of 1 part Sodium carbonate to 6 parts of Sodium bicarbonate. This is then also establishes the buffer system that Tyrone explained. One must just be careful not to add too much of this mixture as this will "harden" the water and too much of this is also not good for soft water fishes.

    Some fishes also do not like low pH such as rainbows which will start developing problems if the pH of the tank water drops below 6.

    Kind regards,

    Dirk
     
    Last edited: Apr 1, 2009
  12. veegal

    veegal

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    I live very near to N1 city and I have the opposite problem - the pH coming out of my tap is 8.8. Very very strange......I'm struggling to bring my pH down so for my Angelfish and Discus.
     
  13. brentnorm

    brentnorm

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    You can also use neutral regulator. Regulates your PH to 7.0
     
  14. Dirk

    Dirk Dwarf Catfish

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    HI Veegal,

    If you live near N1 city, you are most probably getting water from Vogelvlei Dam. Water gets piped from Vogelvlei to Cape Town in cement pipes. This is a standard procedure and there is nothing negative about this for human use. However, if the water as it is found in the dam were to be piped to Cape Town as is, the lower pH of this water would corrode the pipes and they would be damaged quite soon. As a result, the City Council adds lime to the water to increase the pH. Not a lot, but certainly enough to cause it to go up to at least 8.5. This water does however not contain a high carbonate hardness and the amount of acid that might be required to bring the pH down is actually not a lot. I would use standard grade pool acid, which is hydrochloric acid to bring down the pH.

    NEVER add hydrochloric acid directly to the tank, as this could have disastrous consequences as you can have local pockets of very acid water which will severly injure the fish. Prepare the water separately with good circulation and aeration.

    If you are keeping discus and angels, you might actually find that the pH in your tank is already acidified quite strongly as a result of the ammonia and nitrate production and you should check you pH accurately so that you can find out if this is the case. Where I stay in Somerset West, I am constantly fighting against too low pH and my tapwater, which has a pH of 7.5 to 8 is very welcome and I never adjust it. Over and above this, discus and angels can be kept quite happily at a pH of up to 7.5 in any case.

    When keeping discus and angels, brentnorm, one should not use any of the commercial pH stabilizers, such as neutral regulator, as these contain buffer salts which harden the water and for discus and angels you do not want to harden the water.

    Kind regards,

    Dirk
     
  15. veegal

    veegal

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    Wow! Thanks for all that info Dirk - much appreciated!!! I use a digital pH tester so the results are pretty accurate (I hope :) ) I have noticed that after a few days the pH in the tank goes down from 8,8 (tap water) to around 8.0 / 8.1 . It's still too alkaline for the discus though. That being said, I have had no fatalities or problems with keeping either Angels or Discus in these parameters, in fact I've just had a pair of Angels spawn so I guess it's not too bad.

    How much pool acid would you suggest adding to say a 20 liter bucket of tap water, after dechlorinating etc ?

    Also, I think I'm going to make use of all your knowledge about Cape Town water if you don't mind....do you happen to know whether we have chloramine in our water??
     
  16. Dirk

    Dirk Dwarf Catfish

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    Hi Veegal,

    What sort of a pH meter do you use? If it is a hand held model it is not sensitive enough for measurements in the soft water that we have.

    If your fish are fine at this stage, do not try to manipulate the water, just leave it. You can cause far more damage by letting the pH take a dive down or something.

    Both the amount of lime added and the quality of the pool acid will decide how much acid you will need, so I cannot give you an accurate amount. What I can say is that the amount will be small for 20 litres. Remember pool acid is sold for big swimming pools.

    Very, very fortunately, I believe that CT is not using chloramine. As chloramine cannot be remove by aeration as normal chlorine can be, and chloramine can only be neutralized by the addition of something like aquasafe, we must be most grateful that only chlorine is used at this stage.

    Kind regards,

    Dirk
     
  17. veegal

    veegal

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    Hi Dirk, thanks for the speedy response.

    I can't remember the make of the pH meter but it is hand held. Geez and I just bought it a month or so ago and paid an arm and a leg for it :eek:

    I think I'll experiment with the pH in one of my empty tanks for now and just see what the fluctuations are.

    That is great news, about the chloramine, that means I don't have to spend so much money every month on water dechlorinators. I can just age the water overnight running an airstone to remove the chlorine - is that right?? Does that water have to stand overnight?
     
  18. Dirk

    Dirk Dwarf Catfish

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    Hi Veegal,

    Always good to experiment with an empty tank to see how the pH fluctuations will work out before doing any experiments with the fish.

    Yes, you can age your water with an airstone, but I would advise that you do let the water stand overnight at least to get rid of the chlorine as the amounts of chlorine in the tap water in your area can vary quite a lot. I hear this from other persons in your area.

    Kind regards,

    Dirk
     
  19. veegal

    veegal

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    Thanks for all the advice Dirk - muchly appreciated :)

    Regards
    Veronica
     

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