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Oh no, pH crash after DIY CO2!

3K views 19 replies 11 participants last post by  jaidexl 
#1 ·
I started my DIY CO2 this morning on my 5.5 gallon tank. It's a 1.89 L juice bottle with 1.5 c sugar, 1/4 tsp yeast. Only about half the bubbles produced are making it into the HoB filter intake, and it's my understanding that the agitation in the filter is likely losing me even more of the gas. Yet after it's run for about 5 hours, my pH (which was 7.2 a few weeks ago) is down to 6.2. :eek5:

Um...help? I use RO water because it's a small tank with a delicate fish (halfmoon betta, supposed to be more sensitive than other varieties to water parameters) and I have really crappy tap water. I re-constitute the RO with Kent Freshwater RO Right, dosing the amount that's supposed to give me "soft" water. I tested GH and KH of the resulting water once, and for some reason I didn't record the results but I think both parameters were around 40-60 ppm?

Should I add baking soda? How much? Up the amount of GH booster? (I usually prepare about 5 gallons at a time, which is enough for 2-3 water changes and some top-offs.) I'm worried for my fish if I change the water parameters drastically and do a large water change, but I'm even more worried for his long-term health in the acid water (not to mention my poor snail! Now I know why he's hiding!)
 
#2 ·
Sounds like your CO2 levels should be about perfect, then, as the addition of CO2 will always lower pH levels; it happens every time. Most people who use CO2 run their pH low(ish), depending on their original tapwater parameters. I have kept mine as low as 5.60 before, though currently it's around 6.01. A full 1-point drop in pH indicates that a CO2 saturation of roughly 30 ppm, which is ideal for sustaining adequate CO2 levels without harming other tank inhabitants. Sounds like things are going really well, despite your skepticism and worry. Whatever you do don't go dumping things into the tank trying to fiddle with your water parameters...I promise nothing good will happen.
 
#5 ·
A full 1-point drop in pH indicates that a CO2 saturation of roughly 30 ppm, which is ideal for sustaining adequate CO2 levels without harming other tank inhabitants. Sounds like things are going really well, despite your skepticism and worry. Whatever you do don't go dumping things into the tank trying to fiddle with your water parameters...I promise nothing good will happen.
No, trying to fiddle with the params is my last resort! I know it's usually best for everyone involved to let the inhabitants adapt to the water instead of the other way around. But since I'm really trying so hard to pamper this darned fish, and his species prefers a pH of 6.5 to 7.5, the sudden drop really alarmed me! I'll try to take a deep breath, LOL. I guess for today's water change I'll prep the water just as I had been.

Take a cup of yr tank water out and let it sit for 24 hours. If the sample then tests a whole point higher, you're good.
That's a good idea, since part of my worry is that the pH of 7.2 was after my driftwood had only been in there a short while -- I wonder if it has leached more in the meantime and the tannic acid is contributing to the drop. Letting the CO2 dissolve would help to answer that question. But if the pH *doesn't* change much? What else would that indicate besides the tannin issue?
 
#4 ·
Generally a CO2 induced pH drop will not be harmful to fish, the more critical parameter there is KH, which CO2 does not affect. Just watch that your fish aren't gasping for air, particularly in the morning:fish:
 
#7 ·
Halfmoons shouldn't be particularly sensitive unless you got them from a big chain store instead of a breeder. I know they have been tank bread out the wazoo but softer and slightly acidic water would be appreciated.

Like others mentioned the ph change due to carbonic acid shouldn't be a problem for the fish. A ph change due to baking soda or GH booster would be more stressful. The fact that your snail is hiding thought makes me think its lower than you think like over_stocked was saying.
 
#9 ·
Halfmoons shouldn't be particularly sensitive unless you got them from a big chain store instead of a breeder. I know they have been tank bread out the wazoo but softer and slightly acidic water would be appreciated.
No, he's well-bred (parents are from Atison's Bettas) and seems quite resilient, he's just still quite young and I'm overprotective. I would think "slightly acidic" would be a pH around 6.8, and with the logarithmic scale isn't 6.2 several times more acidic than that?

Like others mentioned the ph change due to carbonic acid shouldn't be a problem for the fish. A ph change due to baking soda or GH booster would be more stressful. The fact that your snail is hiding thought makes me think its lower than you think like over_stocked was saying.
I aced this pH/alkalinity/acid-base equilibrium stuff back in freshman chem but that was all about rote memorization of math to me, LOL. I don't think I ever GOT it. Certainly where I sit right now a decade later I don't get why my snail (or fish) would care more about the pre-carbonic-acid pH than about the actual pH of the water he's currently sitting in. I keep hearing it though, that KH matters more than pH, so I'll just trust y'all! :redface: I'll be sure to do the sit-and-test, thanks! :)
 
#8 ·
Letting a sample sit for 24 hrs will degas it of any/all CO2. Whatever it tests at after the 24 hrs is the actual pH of yr tank, including whatever tannins yr DW is adding to it.

Like overstocked says, I too am guessing yr actual pH is now lower than 7.2. Kent's RO Right will add gH, but no kH. Adding a little baking soda will increase yr kH, and counteract the effects of yr DW. If memory serves me, 1/4 tsp in 5 gallons of H2O will raise yr kH 3 - 4 degrees.
 
#10 ·
pH is basically more of a reference to the water's kH, and kH is what your critters actually care about. Adding CO2 to yr water affects the pH, but NOT the kH. That's why we keep telling you pH doesn't mean much, as it moves up and down w/ CO2 levels, even though yr kH remains constant! (well, close to constant, as yr fish waste/detritus/DW acidifies the water, but the kH counteracts/buffers it--until it runs out, THEN yr pH crashes) That's why I recommended adding soda, as RO water will have 0 kH.
 
#14 ·
There are a lot of things that effect pH, people blanket issues as a pH issue, and instantly think each one will kill. There are only a few cases that will lower or increase pH and harm fish at the same time.

1) Rapid TDS/KH/GH fluctuation- happens during a mass dilution or concentration, and they are all affected together in the case of a dilution. Causes osmotic shock in fish, because they're in the water and made of water, like us, it's literally flowing through them, and any rapid mineral related shift is going to wack them out, stress them, and probably kill them.

2) CO2 overdose- desirable CO2 levels will only drop pH about a degree, but it is possible to gas the fish to death especially with a pressurized CO2 setup. This is going to drop pH farther, but it's actually the overdose of CO2 gas that kills them.

3) The obvious and hardly related stuff, like if some poor schmuck accidentally dumps half a gallon of muratic acid into his tank, his pH is going to drop, but his fish are gonna be too busy frying to care about pH.
 
#19 ·
Since I added diy Co2 ph gone from 7.2 to 6 and Kh gone from 1 to 2.
I added 1mm of baking soda and 2mm of calcium sulfate.

Is there anything else I should do?
IMO, messing with your PH with an additive like baking soda is not a good idea. As stated earlier in this message the drop in PH from Co2 will not affect your fish. However, using a additive like Baking Soda to change your PH can indeed affect your fish.
 
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