Another fishless cycle, another pH swing

[nerdelish]

So, I have added another tank to my possession. It's a five gallon tank I plan to use for a Betta.

I'm in the middle of my fishless cycle and my pH has swung. This happened when I was cycling my 29 gallon as well. The difference is that my pH in my 29 gallon dropped significantly from 7.4 to 6.4 ppm. Now, the pH in the 5 gallon is 8.2 instead of the normal 7.4. I assume it's related to my very soft water (3 and 2 KH and GH).

Are there ways to boost my KH and GH that doesn't alter the pH?

Is there something else that could be going on?

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[ScotJudd]

Hi. Normally the cycling process causes Ph to drop if you don't have enough alkaline buffer, a Temperoray buffer measured as Kh. A Kh of 3 is quite low and I would strive to keep it at about 6-10. This does stabilise the Ph but at a higher level but I doubt it would raise yours any higher. I use bicarbonate of soda ( about 2.5 ml per 2 gallon bucket) to raise my tap from almost zero Kh to about Kh of 6. My Ph is steady at around Ph of 7. I also like to balance the Gh to the Kh with Equilibrium, this does not effect Ph.
Your tank seems to want the Ph to rise and the likely culprit is calcium based rocks or gravel in the tank. However, they normally cause Gh to rise as well and yours is not.
At this stage I would be tempted to raise Kh and Gh to about 6-10 and see how it settles out. As your tank is fish less then you can raise the Gh and Kh in one go and see what effect it has. It will not have any negative effect on the filter bacteria.


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[nerdelish]

I will order equilibrium and try it out thanks! I have lava rock, manzanita wood, and white sand in my tank, would any of those raise pH?

When I do water changes, say I remove 2 gallons from my tank, do I add 2.5 ml of it back in or do I have to add up to the whole tank (6.25 ml)?

I only ask because I have heard when you do water changes to add conditioner to dose for the whole tank not just the amount you add back in.

 

[ScotJudd]

Hi again.
If you are asking about altering Kg or Gh then you just dose the water being added to the tank.
If you are talking about conditioner to remove chlorine etc then again you should dose the water being added but some people do indeed dose the whole tank, especially if adding water via a hose which can't be preconditioned. This is normally in much larger tanks though.
If you have no fish then suddenly raising the whole tank Kh or Gh is not a problem. You then just add the appropriate amount of adjuster to any new water. If you had fish in then you would have to increase Kh and Gh more slowly to allow the fish to adapt.


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[nerdelish]

Hi again.
If you are asking about altering Kg or Gh then you just dose the water being added to the tank.
If you are talking about conditioner to remove chlorine etc then again you should dose the water being added but some people do indeed dose the whole tank, especially if adding water via a hose which can't be preconditioned. This is normally in much larger tanks though.
If you have no fish then suddenly raising the whole tank Kh or Gh is not a problem. You then just add the appropriate amount of adjuster to any new water. If you had fish in then you would have to increase Kh and Gh more slowly to allow the fish to adapt.


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That is very helpful information, thank you! I have a 29 gallon with some fish in it, how would you recommend I go about raising the Kh and Gh in a tank with fish?

 

[Fel]

My 20gal fell to about 6.4 when doing a fishless cycle, I dosed it with some potassium bicarbonate and that pumped it up to about a kh of 5 and pH of 7.8 which is much better for establishing bacteria anyway.

Don't forget ammonia will initially raise your pH then once it's converted into nitrites by the AOBs acid is released as a biproduct which will reduce your pH.

So before you have established your AOBs (ammonia oxidizing bacteria) your pH will rise while cycling, once they are actively oxidizing ammonia then you will see the pH begin to fall (or KH if you have a nice buffer)

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[nerdelish]

I had no idea pH would change as a result of ammonia. Thanks for the info!

 

[TbOnE]

So what is the target gh for a pH of 7.8?

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[Fel]

GH (General hardness) is a measurement of other minerals in the water, such as magnesium and calcium to name a couple. This is more of a factor for the type of fish you keep than the pH.

KH (carbonate hardness) is the measurement of your pH buffer, it's generally accepted that a dkh of 4 (4 drops in an api kh test, or 80ppm) is the minimum amount for a fresh water tank.

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