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post #1 of (permalink) Old 03-09-2013, 02:08 AM Thread Starter
Algae Grower
Join Date: Mar 2013
Location: London, Ontario
Posts: 5
Help: Where is the CO2 from my DIY?

Hi Everyone,

Can anyone help a novice to understand why he can't seem to get ~any~ pH drop in response to CO2 injection?

I have a 35 gallon tank with 50 watts of light. I have a bio-wheel type HOB filter. I'm growing beginner plants, most of which seem to be doing well in this limited lighting - Vals, Amazon Swords, Crypt Wendii, Wisteria, "Mat Grass". I can't remember the gravel, but don't think it's anything special. I did recently add some very well rinsed laterite as a top up to the substrate. There is one piece of driftwood and a few non-carbonate rocks.

I'm currently running DIY CO2 into a Hagen ladder. I started with two 2 litre pop bottles, but have since added two more 1 litre bottles. All of them "T" into the Hagen ladder. I get from between 0.5 to 3 bubbles per second, depending on how long the bottles have sat. (I actually added the 3rd and 4th bottles to try to push enough gas pressure for a wood air stone, which I was able to do).

I know that the ladder isn't as efficient as a diffuser or an inline reactor. However, the bubbles enter the ladder at about 5mm in diameter and exit at about 1 mm. This tells me that most of the gas is dissolving (right?). I've tried placing the ladder in different parts of the tank - beside the filter and as far a way as possible from it.

I also tried bubbling the gas through the wooden airstone for a few days. The bubbles were relatively fine, and I let them climb up the ladder. I removed the airstone when no pH change was happening.

I have 10 cardinals, 4 platys and an OttoCat.

Water Chem
pH - 7.6
hardness - 80-100 mg/L
kH alkalinity - 100 mg/L (kH about 6 degrees)
temp - 78F
25-40% water change per week.
(all test kits are API and brand new).

I dose nutrients on a low-tech "as needed" basis. I test and try to target nitrate = 10-20 mg/L, Phosphorus = 0.5 mg/L, Iron=0.25 mg/L. Flourish micro added 1-2 times per week.

Shouldn't I at least be seeing some pH drop due to the gas injection? I know that the Hagen ladder isn't that efficient, but from what I've read it isn't THAT bad either. I should be seeing something right? The pH-KH chart tells me that I hardly have any CO2 at all.

I should mention that this was a long established, but very undermaintained tank for several years. I just did a major gravel clean up in January, with two 80% water changes. The fish survived. There were only a few living Vals and mat grass at the time. I added the Amazon Swords and Crypts in early February. I actually did have lower pH for several days shortly after this rebuild (dropped to about pH=7, though on an older pH kit), and actually had pearling (streaming of bubbles from the newly planted Amazons and even some of the Vals), but this has since stopped.

The plants are doing well, with two Amazon swords having grown to the canopy. Algae is under control. So I guess this is "success". But I would like the CO2 to work, so I can someday try some more challenging plants.

Any ideas?


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