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Thread: 6.5ph

  1. #1
    Jumbo sacicu's Avatar
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    6.5ph

    For the past 6 months I have been running my new pond of around 37 tons with 11 jumbo and near jumbo gosanke koi ( now only 10 after selling one) at around 6.5ph water readings.

    Has my pond experience PH swings? No. readings taken from morning to night showed same readings.

    Has my koi lost their appetite? No. They all have continued to have appetite and are growing.

    Has the low Ph resulted in bouts of string algae growth? Yes there was a healthy growth of string wall algae for some time which eventually disappeared after I salted the pond for awhile. Since I now increased the percentage of water change the string algae has not come back so far.

    What is the effect of the lower Ph on my pond? Personally I can see that the skin and beni of gosanke has become more softer without any effect on the coloration. At lower PH, there will be always be a small ammonia reading on the test kit but my nitrite and nitrates are zero. This shows that ammonia eating bacteria does not multiply as fast in low PH. However, ammonia readings when equated to low PH means is very safe in toxicity. Interestingly Ive experimented also dropping 500 grams of baking soda which slightly raised the Ph and immediately the ammonia reading was suddenly down.

    Has the low KH impaired the development of sumi? Not at all. On the contrary, the sumi improved in some koi.

    Has low PH impaired healing of Koi? I do not think so. I had one jumbo kohaku that suffered from swim bladder episode after 3 yrs of gulping issues and had ulcer at the side and bottom. After several injections of antibiotics and treating the skin ulcers at the bottom and sides, the koi recovered. The swim bladder issue is gone. Its gulping issue was gone. Its injuries healed in 2 weeks and its appetite was remarkable back.

    They say that the koi's blood PH is 7.4 to 7.5 and putting koi in constant low PH environment causes acidosis with koi loosing appetite, koi staying on the bottom, red streaks on body and fins. Personally, I have not observed this at 6.5ph nor at 6ph.

    Is there a danger of a PH crash running pond at 6.5ph. Yes definitely. However, I do regular water change and total flushing of submerged filters twice a week enough to put in enough alkalinity to manage a constant 6.5ph readings. I would not advise running low ph if you are not alert and do not know how to manage it. I once tried running the pond water at a dangerous 6ph for a month but I feel comfortable at 6.5ph. In my old smaller 21 ton pond where I kept the 11 koi, I was more comfortable running it at 7 to 7.2ph level due to the higher stocking levels.

  2. #2
    Daihonmei MikeM's Avatar
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    I do not believe a particular pH is as important as stability. At a pH of 6.0 - 6.5 much of the ammonia will be in the harmless ammonium form. Any improvement in skin and pigment may be result of minimization of exposure to harmful ammonia. It has been suggested in the aquarium hobby that the ammonium form is less harmful than nitrate. (Dealing with low pH tropical fish which have great sensitivity to ammonia, nitrite and nitrate.) It is easier to maintain pH stability when it is above 7.0 and the water is moderately hard, but you have found a way that works for you, so 'no problem'.

    ....How soft is your water? It's well-established that koi skin and pigments do best in softer water.

    There might be something to the idea of acidosis, etc. occurring in a truly low pH... say, 5.0 or lower. I think of a pH of 6.5 as being in a moderate range. I have seen pH readings of some Niigata mud ponds at 6.2 to 6.8 without any problems reported. Of course, mudponds have natural processes that maintain stability.

    How long have you been maintaining a pH of 6.5?

  3. #3
    Jumbo sacicu's Avatar
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    Quote Originally Posted by MikeM View Post
    I do not believe a particular pH is as important as stability. At a pH of 6.0 - 6.5 much of the ammonia will be in the harmless ammonium form. Any improvement in skin and pigment may be result of minimization of exposure to harmful ammonia. It has been suggested in the aquarium hobby that the ammonium form is less harmful than nitrate. (Dealing with low pH tropical fish which have great sensitivity to ammonia, nitrite and nitrate.) It is easier to maintain pH stability when it is above 7.0 and the water is moderately hard, but you have found a way that works for you, so 'no problem'.

    ....How soft is your water? It's well-established that koi skin and pigments do best in softer water.

    There might be something to the idea of acidosis, etc. occurring in a truly low pH... say, 5.0 or lower. I think of a pH of 6.5 as being in a moderate range. I have seen pH readings of some Niigata mud ponds at 6.2 to 6.8 without any problems reported. Of course, mudponds have natural processes that maintain stability.

    How long have you been maintaining a pH of 6.5?
    Its now been 6 months. I ran it at 6 ph for a month also. I run my discus aquarium tank also at 6ph. Never had a ph crash.

  4. #4
    Honmei ricshaw's Avatar
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    Living in Southern California, I cannot relate to keeping Koi where the pH is 6.5.

  5. #5
    Jumbo Akai-San's Avatar
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    Stabilizing pH at 7.0 has always been my nemesis. I have introduced oyster shells and coral within my filtration process, but still the only way I can increase pH is through continued water changes as our Hawaii source water is higher pH (8.0+). Even with the water changes, I have been maintaining pH levels between 6.5 - 6.8 consistently. Unless I do a 40% water change (by accident), my pH doesn't go past 7.0.

    I didn't know that string algae is attracted to low pH. That is a good reason to keep pH up for sure.

  6. #6
    Jumbo sacicu's Avatar
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    I was wondering if ammonia is being converted to harmless ammonium. Does this mean that there is less biological conversion necessary from ammonia to nitrite to nitrates as compared when ammonia is not being converted because of low ph? And if so, does this ultimately result in lower nitrates?

  7. #7
    Tosai
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    Quote Originally Posted by sacicu View Post
    For the past 6 months I have been running my new pond of around 37 tons with 11 jumbo and near jumbo gosanke koi ( now only 10 after selling one) at around 6.5ph water readings.

    Has my pond experience PH swings? No. readings taken from morning to night showed same readings.
    How do you buffer at pH 6.5?

    Are there buffers other than sodium bicarb that are safe for koi ponds? Sodium bicarb buffers at pH 8.3. Or do we need carbonate buffering because of CO2 being released by fish and algae (at night) and being produced by algae during the day?

    My source water has a pH of close to 8 out of the tap but very close to 9 once CO2 is at equilibrium for temp and barometric pressure. I am keen to pre-treat my water such that my ponds are at pH 7.5 or close to that. I was thinking of using hydrochloric acid to consume kH already in the tap water and push pH down to 7.5. But how do I buffer at 7.5 before running the water into the ponds?

  8. #8
    Jumbo sacicu's Avatar
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    Quote Originally Posted by Jacques View Post
    How do you buffer at pH 6.5?

    Are there buffers other than sodium bicarb that are safe for koi ponds? Sodium bicarb buffers at pH 8.3. Or do we need carbonate buffering because of CO2 being released by fish and algae (at night) and being produced by algae during the day?

    My source water has a pH of close to 8 out of the tap but very close to 9 once CO2 is at equilibrium for temp and barometric pressure. I am keen to pre-treat my water such that my ponds are at pH 7.5 or close to that. I was thinking of using hydrochloric acid to consume kH already in the tap water and push pH down to 7.5. But how do I buffer at 7.5 before running the water into the ponds?

    I do think the reason why I am able to hold it steady at 6.5ph is because of the low stocking levels I have and the regular twice a week flush and water change of 20% a week which keeps enough Kh just to maintain the low ph level. In the event of heavy rain, I would change more water to add back some more kh.

    Personally I think in your case, the best is to just go for water softener and leave whatever ph it is. I know of a hobbyist who grew a kohaku to 97cm when the koi was just turning gosai. The koi's skin was still outstanding despite the fact that he had hard water which he softened using a water softener. However his big pond was very lightly stock so there is not much ammonia buildup even when Ph is high.

  9. #9
    Daihonmei MikeM's Avatar
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    Quote Originally Posted by sacicu View Post
    I was wondering if ammonia is being converted to harmless ammonium. Does this mean that there is less biological conversion necessary from ammonia to nitrite to nitrates as compared when ammonia is not being converted because of low ph? And if so, does this ultimately result in lower nitrates?
    Basically, yes. It gets complex (doesn't everything about water?). The ammonium is still available for algae (string algae, carpet algae and greenwater algae). In fact, the ammonium ion is preferred. As long as the pH does not get lower than the range the algae present need for their functions, the higher proportion of ammonium favors algae growth. That means the ammonium can get 'eliminated' (consumed by algae/plants) without being converted to nitrite/nitrate. Nitrification is a slower process the lower the pH goes. It is often said that nitrification ceases at a pH below 6.5, but some studies indicate that this is not quite accurate. Where there is a mature biofilm a higher pH can be maintained within the biofilm and the nitrifiers can continue, but at a much reduced rate. So, some nitrate may eventually be detected, but may need a very sensitive test to detect it.

    While ammonium is generally considered harmless, it is something of a ticking time bomb. Anything increasing the pH risks sudden conversion to deadly ammonia... like algae producing lots of O2 at peak photosynthesis while aeration rids the water of dissolved carbon dioxide. The chemistry of the water causing the low pH is fundamental. So, what applies to one pond can be wholly irrelevant for another.

    Seems to me that you are in a great place with your system. You have dealt with the lower pH for 6 months+, have a regimen of water changes that works for you without more labor than you are willing to expend and your koi are doing at least as well (and perhaps better) than previously. ....Great example of why the general recommendations we are used to seeing always have to be understood in context.

  10. #10
    Jumbo sacicu's Avatar
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    Quote Originally Posted by MikeM View Post
    Basically, yes. It gets complex (doesn't everything about water?). The ammonium is still available for algae (string algae, carpet algae and greenwater algae). In fact, the ammonium ion is preferred. As long as the pH does not get lower than the range the algae present need for their functions, the higher proportion of ammonium favors algae growth. That means the ammonium can get 'eliminated' (consumed by algae/plants) without being converted to nitrite/nitrate. Nitrification is a slower process the lower the pH goes. It is often said that nitrification ceases at a pH below 6.5, but some studies indicate that this is not quite accurate. Where there is a mature biofilm a higher pH can be maintained within the biofilm and the nitrifiers can continue, but at a much reduced rate. So, some nitrate may eventually be detected, but may need a very sensitive test to detect it.

    While ammonium is generally considered harmless, it is something of a ticking time bomb. Anything increasing the pH risks sudden conversion to deadly ammonia... like algae producing lots of O2 at peak photosynthesis while aeration rids the water of dissolved carbon dioxide. The chemistry of the water causing the low pH is fundamental. So, what applies to one pond can be wholly irrelevant for another.

    Seems to me that you are in a great place with your system. You have dealt with the lower pH for 6 months+, have a regimen of water changes that works for you without more labor than you are willing to expend and your koi are doing at least as well (and perhaps better) than previously. ....Great example of why the general recommendations we are used to seeing always have to be understood in context.


    Is it possible why my wall algae blanket weed used to grow fast is because of the ammonium buildup due to low ph? I have this problem in my aquarium now, the blanket weed grows very fast.

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