Modest pH decrease after cleaning filter

[PNWaquarist]

After doing a 20% water change, I cleaned my filter yesterday morning. Before cleaning the pastic filter pieces with Q-tips, I stored my filter media in a large cup of tank water. I then squeezed the sponge filter piece in the bucket of spent tank water about 6-7 times and moved my charcoal media into my quarantine tank for cycling. I did not mess with the porous ceramic media and kept it in tank water throughout the process.

As I typically do the day after cleaning my filter, I checked my water parameters this morning. Ammonia and nitrites were both 0 ppm, but my pH dropped from its usual value of 7.3-7.4 to about 7.0. The test solution color definitely had a more greenish hue to it than usual. I don't think that my tap water pH has changed, as I just set up a 10 gallon quarantine tank a couple of days ago and its pH was ~7.5 yesterday (after it had a good 12 hours to equilibrate with the atmosphere).

Has this happened to anybody else? I'm wondering if the removal of my charcoal media, the squeezing out of my filter sponge, and the wiping down of the inside of my filter took enough BB out of the filter that more is regrowing and lowering the tank pH... but that there is still enough BB elsewhere in the tank to process the ammonia and nitrite present.

 

[ScotJudd]

There are so many variables that effect Ph that it's not easy to give you a definitive reason. My tank Ph, when fairly new, sat at about 7.5. A year later it is fully planted and stocked and Ph sits reliably at about 6.8. My tap water has not changed. Providing your Ph doesn't swing wildly then I wouldn't be too concerned. It might be worth checking your Kh if your Ph continues to drop. A low Kh can allow Ph to crash. This might not be the case for you but I found initially that my Tap Kh was <1 and had be be buffered to about 6 to give stability.


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[trennamw]

I think you're already aware of the KH issues we west-of-cascades Oregonians face ... Hard to say what happened but maybe something tossed out enough acids to cause a little drop the KH couldn't buffer fast enough.


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[PNWaquarist]

This is true. Water here does not buffer all that well and it's a good idea to periodically monitor one's tank pH.

My best guess is that my tank is undergoing some sort of mini-cycle, where there is enough acid-producing BB growing in the filter to lower the pH a little. Thankfully, I appear to have a robust enough BB colony outside of my filter to handle my fish's bioload. My fish were behaving normally today. I'll do my regularly-scheduled second 20% WC of the week on Sunday and re-measure the tank pH a while afterwards.

 

[trennamw]

What is your KH ? And do you do anything to adjust it?

In Portland it's 0.1 degrees or less. After trying many things I started throwing 1/4 tsp each Seachem Equilibrium and API Chiclid buffer for every 4(ish) gallons of water. It puts GH and KH about 3-4 and I have wonderfully stable pH now.


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[PNWaquarist]

I'm around 2.5 degrees of KH (roughly 40 ppm of total carbonate). I used to add small amounts of baking soda, but (1) it raises the pH and (2) my pH has historically been rather stable when using untreated tap water.

 

[trennamw]

I have little pH drops unless I get KH to 3 or 4. Since you're so close maybe all you need is a tiny bit of crushed coral.

Or nothing, if you only get these tiny and rare swings.

Baking soda really wants to buffer pH to 8. The Chiclid buffer I use heads that direction as well, one ingredient is baking soda. They'd probably both buffer more than you wish and the pH would go up further than you want.


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[ScotJudd]

It is true that baking soda raises Ph, however, if you are using Co2 which results in Ph dropping (including the Co2 released by plants at night) then using bicarb to give a Kh of around 6 deg doesn't give rise to high Ph readings. My tanks are Kh 6, Gh 6 and Ph 6.8 with a tiny movement depending on the time of day. I would think that without Co2 I would aim for about Kh 3.


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