Stable PH and co2 question - The Planted Tank Forum
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post #1 of 6 (permalink) Old 06-25-2020, 04:57 AM Thread Starter
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Stable PH and co2 question

I’ll start by explaining what’s happening in my tank, I’ve noticed I’ve been getting ammonia, it’s been set up for around 4 months already and was cycled, but I raised my co2 levels to try to get a lighter green on my co2 level indicator since my tank is heavily planted, one of the times I tested my water the ph seemed to be around 5.5 according to the colors on the tests, This is obviously too low so I’m thinking this is killing the beneficial bacteria that turns ammonia into nitrates, my question is, for those of you who keep co2 levels around 30ppm, how do you keep your ph from getting too low? I don’t want my gh to be too high, I think a high gh would make a higher ph but I want a low gh around 4 and good co2 levels without the crazy acidic PH.
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post #2 of 6 (permalink) Old 06-25-2020, 08:43 AM
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Think that u just need to buffer your Kh. Don't know did u test it already? If Kh is low than ph fluctuate a lot with injecting co2. Mine is around 7 dkh and my pH drops on 6,3 with yellow drop checker.
U can buy a Kh buffer in any local fish store.
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post #3 of 6 (permalink) Old 06-25-2020, 01:05 PM Thread Starter
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Yeah that seems correct, everyone is saying the same thing and yes, my KH seemed to be at zero which is bad, I added some alkaline buffer hopefully it’ll help. I mix my own water and wasn’t adding any alkaline buffer, didn’t think KH was so important. Is just that I’ve seen people have very low kh cause of their shrimp, and still have good co2 levels without ph getting lower than 6.5.

Thanks for the reply 👍
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post #4 of 6 (permalink) Old 06-25-2020, 07:39 PM
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Below 6.8PH at normal 75 temps almost all your ammonia compounds exist as ammonium, which is at least 50x less lethal than pure un-ionized ammonia. As temp increases the ammonia:ammonium ratio increases, the warmer the tank the more exists in legal ammonia at a particular PH.

Take a glass/jar of tank water, let it set out for 24hrs, test PH, that is your tanks degassed PH, test again at 48hrs for good measure.

Here is a site that lets you calculate actual free ammonia. Measure your PH and ammonia levels right before co2 shuts off and again right before co2 comes in morn. Enter in stats in for both periods and correct temp and it will tell you how much lethal free/un-ionized ammonia you have in solution across the days cycle. Only if your ammonia/ammonium ratios spike beyond what your bio-media surface area has capacity to handle will you get troublesome ammonia spikes.

Free Ammonia Calculator (Javascript)
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post #5 of 6 (permalink) Old 07-04-2020, 12:22 PM
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Originally Posted by Alien87 View Post
I tested my water the ph seemed to be around 5.5 according to the colors on the tests, This is obviously too low.
This is correct. Ph below 6 stops all oxidation of ammonia in your filter. You could use crushed coral to get you ph back to 7-7.4. Only need about 2 tablespoons full to last your tank forever. Put it in a mesh bag and drop it in your tank or filter. Make sure you change/replace it about every 3 months.

Last edited by Somefishguy; 07-18-2020 at 04:15 PM. Reason: added more data
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post #6 of 6 (permalink) Old 07-06-2020, 02:15 PM Thread Starter
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I’ve been doing more research and found a PH of 5.5 isn’t bad, depending on what plants we keep, so I’m assuming this means the PH being this low won’t kill any bacteria. Some plants actually like the water that acidic. I’m aiming for around 6.5 though. But yeah I’m using Amazonia so it keeps bringing it down, I need to add Alkalinity buffer more often.
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