DIY Co2 75 Gallon - PH drop and major impact within 24 hours? - The Planted Tank Forum
 
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post #1 of 6 (permalink) Old 05-19-2014, 01:17 PM Thread Starter
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DIY Co2 75 Gallon - PH drop and major impact within 24 hours?

24 Hours ago I set up a DYI Co2 system with two 2 Liter bottles, two cups of sugar and one tablespoon of yeast per bottle. I had the tube sitting in the tank and within twenty minutes, 6 to 10 bubbles per second started streaming out. I attached an air stone and placed it directly under my 1000 gph power head. Soon after, the water was filled with little air bubbles and they started gathering on the top.

The tank is a 75 gallon tank lightly planted with two angel fish in it. It almost appears as if the fish are now struggling. They wont come to the surface to eat and their gills are moving 100 mph. I check all my water parameters and for the most part, everything seemed fine. The PH however had a major drop. My PH right out of my tap is 7.6, but this morning in the tank with the co2, the PH is now 6.4. I posted another questions regarding my test kit and received some advice on how to calibrate it. I calibrated for the PH and again, the reading is still 6.4.
I always thought that a DIY co2 on a tank this size would have very little impact, but I figured Id give it a try anyways as I already had all of the required items.

Is everything normal here given the info I have provided?
Also, should I be pulling the tube out of the tank in the night when the lights go out?
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post #2 of 6 (permalink) Old 05-19-2014, 03:23 PM
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You used a huge amount of yeast, so you are getting a huge amount of CO2, but only for a very few days. More usual amounts of yeast per 2L bottle are 1/4 to 1/2 tsp per bottle. With that amount, you get far less CO2, but it lasts for 2 weeks or so.

Your big pH drop indicates that you have around 30-40 ppm of CO2 in the water, possibly less. With that amount it is possible that the fish are uncomfortable.

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post #3 of 6 (permalink) Old 05-19-2014, 03:53 PM
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Where is your KH and GH sitting? They might be to low to help buffer your pH. Also are you running an air pump into the tank?

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post #4 of 6 (permalink) Old 05-19-2014, 04:12 PM
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Some run air wands at night to help gas off CO2 when the light is out since DIY systems run 24/7. I think you will see a sharp decline in the bubble rate very soon. I run pressurized CO2 on my 75g and have it set at to about 5 bps (very difficult to tell at that rate) and it stays on for 9hrs and I get about the same amount of ph drop.

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post #5 of 6 (permalink) Old 05-19-2014, 08:07 PM Thread Starter
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Quote:
Originally Posted by Hoppy View Post
You used a huge amount of yeast, so you are getting a huge amount of CO2, but only for a very few days. More usual amounts of yeast per 2L bottle are 1/4 to 1/2 tsp per bottle. With that amount, you get far less CO2, but it lasts for 2 weeks or so.

Your big pH drop indicates that you have around 30-40 ppm of CO2 in the water, possibly less. With that amount it is possible that the fish are uncomfortable.
This is my first attempt at doing any type of Co2 and my understanding is that 30 ppm is the ideal amount.

Quote:
Originally Posted by Xarieck View Post
Where is your KH and GH sitting? They might be to low to help buffer your pH. Also are you running an air pump into the tank?

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I don't have any way to measure my kh or gh. No air pump in the tank.

Last edited by Darkblade48; 05-20-2014 at 01:04 AM. Reason: Back to back posts
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post #6 of 6 (permalink) Old 05-19-2014, 09:35 PM
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GH has no effect on pH. KH affects pH, but is not a buffer. Higher KH means higher pH, but the change in pH with CO2 is the same, no matter how high the KH goes. 30 ppm may be a good number for some tanks, but may be too little for others, and possibly too high for tanks without good oxygen content in the water.

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