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  1. #1
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    Fishless cycle: low KH, pH crash

    This is day 11 of fishless cycling my new 38g. I seeded the tank with filter media + gravel from my 10g. The filter on the new tank is a Penguin 350. Decorations include gravel, plastic plants and a piece of driftwood.

    I use AP's master + GH/KH kits.
    My tap water readings are pH: 7.4 KH: 3dH GH: 3dH (reading after 24 hours).

    Nitrite started showing on day 3. It has risen but then has remained pretty steady between 2 and 2.5 for the last 6 days. Nitrate is also steady at around 6ppm for the same time. Ammonia finally dropped today to 0.1. I add 10ml daily since day 3.

    pH has decreased gradually - from 8 on day 1 to 6 today. kH dropped as well to a reading of 1 dH yesterday and today. I added some baking soda on both days, raising it up back to 3 and also raising pH back up slightly (until it dropped again).

    Should I keep adding baking soda on a daily basis now? Or should I add a lot, raising the KH to a higher level, hopefully increasing pH? Is there anything else to do?
    I found some threads about the issue, and I am aware of a problem with low KH values. I'm just not sure what the best approach is (if there is such).

    Also, is it ok to leave the driftwood in the tank?

    Thanks,
    Gali





  2. #2
    Purple is the color of Royalty daveedka's Avatar
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    I don't actually know which way is better or if it matters, I used baking soda to target mine at 5 dKH and my tap water was pretty much the same as yours. By raising it to 5 it seemed to hold steady at a safe level for several days at a time. I travel through the week, and in 5 days it would drop from 5 down to 3 and then I'd bring it back up. Just my personal experience, I know it worked, but don't know if there is a better way.
    Dave



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    Without fish, I don't think you need to worry much about pH crashes and KH while your tank cycles. Do you plan on adding CO2 when the tank is up and running? (This is something worth worrying about when the fish are there, though)

    Also, did you boil and soak the driftwood before adding it your tank? Chances are that the tannic acid from the driftwood maybe contributing to the breakdown of the KH.


    HTH
    Last edited by benedictj; 03-22-2005 at 11:59 PM.



  4. #4
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    Actually, you DO need to worry about pH and KH crashes during fishless cycling. When pH and KH drop, the nitrifying bacteria slow down/stop multiplying. Adding enough baking soda to keep 3-5 degrees KH in the tank will avoid this problem.

    Jim



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    Quote Originally Posted by benedictj
    Without fish, I don't think you need to worry much about pH crashes and KH while your tank cycles. Do you plan on adding CO2 when the tank is up and running? (This is something worth worrying about when the fish are there, though)
    This is incorrect. A pH crash can have very negative effects on the bacteria causing the cycle to either slow down or stall out completely. I'd assume if the pH was allowed to drop low enough, at some point the bacteria would even start to die off.

    Using baking soda is a cheap, easy and fast way to keep the KH up during a fishless cycle. In most cases, once the tank is established, your regular weekly water changes are enough to replenish the KH and keep the pH stable.



  6. #6
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    Quote Originally Posted by ArkyLady
    This is incorrect. A pH crash can have very negative effects on the bacteria causing the cycle to either slow down or stall out completely. I'd assume if the pH was allowed to drop low enough, at some point the bacteria would even start to die off.
    Look, I completely understand everyone's concern about bad advice being dispensed, but if you look a little deeper you'll see that ultimately it isn't bad or uneducated advice at all...

    First and foremost, all water will reach equilibrium. The notion that an adequately filtered tank will reach a pH that is so acidic that it kills cycling bacteria is a stretch. If this were the case, hobbyists wouldn't have blackwater tanks. Also, for our intents and purposes the difference in consumption at 5.8 and 7.8 are virtually impercievable, it would take a lab to determine the difference.

    I will admit that it was a misnomer for me to call descending pH ph crash. In this case we truly are talking about descending pH since it has obviously been gradual over a 6 day period. Anyway, if the arguement is that cycling bacteria are adverse to extreme swings in pH, than it is equally detrimental to increase the pH from 6 to 7. I don't think anyone here would advocate using a product like pH up or pH down because of the yo-yo effect, so why emulate the same effect now and risk it?

    Also, and obviously, the low pH isn't causing problems. The ammonia is being converted to nitrite, the cycle seems to be working. Why risk impeding it by messing with the parameters?



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    Ignorance speaks so loudly. The nitrification bacteria in our tanks grow and multiply very slowly at pH 6.0, and arrest at about 5.5. If you not know, please don't try to justify incorrect statements. It is common to have pH declines during fishless cycling as the KH is used. It is equally common for folks in that situation to go into very extended cycles with no progress at all if their starting KH is low and if they do not partial to restore that, or supplement KH to correct it. You can test that be doing a search and seeing the many many threads comparable to this one, but with weeks of no progress. The correction of the KH by partials or by sodium bicarbonate always restarts the process. Besides which, most folks here know better that to suggest additives such as pH up or down - they don't work well enough to be bothered with.

    Water will reach an equilibrium? Where? At KH=0? That will not support either nitrification or fish. Get a life, and while doing so, learn a little.



  8. #8
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    Thanks, everybody!
    I just wanted to make sure I wasn't doing something I shouldn't, as adding baking soda on a daily basis didn't seem right.
    Ammonia is at 0 tonight, Nitrite is dropping as well. After adding baking soda this morning my KH is up a bit and pH is also higher at 6.4.
    I'll keep doing the same. Hopefully my tank will be cycled soon



  9. #9
    Purple is the color of Royalty daveedka's Avatar
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    Just for the record, a rapid but reasonable jump in Kh and Ph won't harm the cycle at all. With no fish in the tank it will not hurt to boost your KH to say 5 dKH quickly. For me, one teaspoon of Baking soda raised KH 1 dkh in 30 gallons of water. I'd boost it to at least 3 quickly if it were my tank, simply because 3 is sort of the nomal minimum safety level that most of us like to see.
    HTH
    Dave



  10. #10
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    I agree. I'd chunk in more baking soda, too. It won't hurt your fishless cycle to get pH up a bit, either, which will also occur with more baking soda.

    Additionally, boosting your tank temp up to 86 or 88 degrees F will speed up the cycle a bit.

    HTH,
    Jim



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