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  1. #1
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    PH keeps dropping.

    I have read several threads on PH and have a question that still stumps me. My PH in my system drops from a 7.8 to a 6.0 in about 5 days. I have a 500 gallon system that cirrculated for 1 week without fish and before cycling. It did not change then, so I am confident its not the grow media or water.
    I have about 50 young fish, and about 50 minnows and a few crawfish in there right now. A have a piece of coral from a salt water fishtank that I added after the PH started dropping, and the rest is plastic fake plants. I struggle feeling them pellets due to the catfish only eating at night, and crappie not eating good, so there is leftover food in there, but the crawfish take care of that in time.
    I use calcuim carbonite, and potasium carbonite to raise it when needed.
    I have had the system going for a few months now. I guess my question is could this PH dropping still be from bacteria multiplying, or something else?? NH2 and nitrites are always 0. Nitrates stay around 40PPM. I do add new minnows that I catch from the ditch?? Anyone have any ideas?
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    “We must reject the idea that every time a law’s broken, society is guilty rather than the lawbreaker. It is time to restore the American precept that each individual is accountable for his actions.” – Ronald Reagan

  2. #2
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    Re: PH keeps dropping.

    1 week? did you dose with ammonia? if not, then you were just running water through your system, not "cycling" - the process takes anywhere from 6-12 weeks, and depends on a number of factors..
    the nitrification process does indeed cause the ph to drop, i use "hydrated lime" to buffer, and have used shellgrit and eggshells in my growbeds to keep the ph at about 7.2 or so..
    when your ph drops below 6 (the api test kit only goes down to 6) your bacteria colonies can "crash"....(not a good thing)
    and then you basically have to begin cycling all over again..

  3. #3
    Members Aloha Don's Avatar
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    Re: PH keeps dropping.

    Also had this PH problem.
    Keith's recommendation of shell grit works great.
    I picked up sea shells, cleaned and crushed them and added to the system under the flowing water and in GBs.
    The PH slowly buffers up to about 7 - 7.2
    Dont want to raise it too quickly. Too much of a shock on the entire system.
    Put all excuses aside and remember this: YOU are capable - Zig Ziglar

  4. #4
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    Re: PH keeps dropping.

    I ran the water though system for a week before I started cycling just checking my plumbing. The PH did not budge. I would guess I am still in the cycling process, but I understood that once your Ammonia and Nitrites are 0, your good. I will try the eggshells, should I keep them in a sack, of just put them in the bed itself??
    “We must reject the idea that every time a law’s broken, society is guilty rather than the lawbreaker. It is time to restore the American precept that each individual is accountable for his actions.” – Ronald Reagan

  5. #5
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    Re: PH keeps dropping.

    when i first used shellgrit i put it in a sock, and it hung so that the growbed drained over it,, when i redid all my growbeds, i just put it right in the bed, under several inches of media

  6. #6
    Members bsfman's Avatar
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    Re: PH keeps dropping.

    If, as you say, your system has been cycled for a few months and you've experienced a sudden pH drop, it could be due to rain water which can often be quite acidic. A handfull or two of crushed oyster shell in a sock should bring the pH back up slowly.

  7. #7
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    Re: PH keeps dropping.

    Thanks alot for the advice!!! I will try them soon. My system is in a greenhouse, no rainwater. So I guess I will chalk it up to still cycling, its been about 2 months.
    “We must reject the idea that every time a law’s broken, society is guilty rather than the lawbreaker. It is time to restore the American precept that each individual is accountable for his actions.” – Ronald Reagan

  8. #8
    Moderator JCO's Avatar
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    Re: PH keeps dropping.

    I second the crushed shells in the grow beds.
    JCO
    Irish eyes are always smiling but
    • "In the eyes of the world, you are only as good as your last success"
    so never forget
    • "MAN IS ONLY LIMITED BY HIS IMAGINATION"

  9. #9
    Aquaponics 101 Oliver's Avatar
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    Re: PH keeps dropping.

    I don't see any aerators in your fish tank. As your fish grow and produce more waste, you will need more aeration than what it appears you now have.

    From my experience, the bacteria start to crash as the pH goes below 7.0.

    In a functioning cycled system, you will always show an ammonia and nitrite reading around 0.25. This is an indication that the fish are pumping out ammonia and it is being converted on a continuous basis. With ammonia at zero, the cycling has halted; for there is nothing pushing the bacteria to multiply.

    We have also seen that if there are not enough plants in the grow beds, then the pH will start to drop and no amount of Potassium Hydroxide or Calcium Hydroxide will keep it up. I'm not sure what the mechanism is that causes the pH to drop when the plants are too few but we have seen this repeatedly. Filling the grow beds with plants solves that problem.

    On the other hand, too many plants will cause a Nitrate drop and plants growing massive amounts of roots in search of nutrients.

    Oliver
    To measure is to know

  10. #10
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    Re: PH keeps dropping.

    I dont have any live plants in my system, only plastic plants for show. My tank is situated in my greenhouse to where to sun does not hit it. I did not think plants would grow without direct sunlight?? What are yall thought on that?? Should I try live plants without sunlight?
    I do have a big aerator in there with two outlets, just cant see it from the pic.
    I have seen my Ammonia come up to .25 here and there, but not consistently. I am always adding new minnows hoping they will begin to reproduce, so lots of fish waste going in.
    I will start putting eggshells in there right away.

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