Why are people recomending co2 over 30ppm? - The Planted Tank Forum
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post #1 of 9 (permalink) Old 02-23-2005, 11:03 PM Thread Starter
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Why are people recomending co2 over 30ppm?

Ive noticed more recently suggestions of raising co2 levels to 30+ to even 50ppm. A couple years ago 30ppm was the redline as a precaution for fish health. What has changed and what are the determining factors for these levels? Are fish not bothered by 40ppm of co2 anymore?
Its starting to seem like people are now keeping the tanks for plants and the fish are the decorations which is fine but...... Dosing hard, adding nitrate to 20-30ppm isnt this a totally unnaturally high level? I know nitrates are not good for animal health. If its a plant only tank I can see turning your water into a potent fertilizer, but for me I like to use as little as needed when it comes to adding nutrients to the tank.
OK sorry for the rant
Any who I am not a biologist or in medicine so I dont know, but does anyone else here really know what a safe level is?
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post #2 of 9 (permalink) Old 02-23-2005, 11:42 PM
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I think that the people that recommend very high CO2 levels are in the category more must be better. Recently due to a faulty Kh test kit I was over revving my CO2, I didn't notice any increase in plant growth at all. Yes there was more pearling but the fish were unsettled and my Ph was lower than I liked.

I've halved my bubble rate now, the plants are tremendous and the gas tank will last twice as long.

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post #3 of 9 (permalink) Old 02-23-2005, 11:59 PM
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The 30ppm of CO2 and dosing heavily is mostly contributed from Tom Barr's EI method. An analogy I'm stealing from someone (sorry can't remember who) is that EI shoots as many arrows at the target, hoping one will hit the bull's eye. The bull's eye being healthy plant growth, no deficiencies, etc. Using large weekly water changes are important with this method to keep the fertilizers from building up out of control. "Resetting" the tank if you will.

There is an excellent discussion on exactly on why high CO2 on Barr's forum. Here's a quote:
Originally Posted by Tom Barr
There's some debate about the charts, we use something quite different in the lab. I do suggest using the chart as a guide, but you are not bound to it. Adding more CO2 often does not hurt and solves something issues many folks have.
Also I'd like to add that test kits can provide a lot of error. Those regent based pH kits measure in increments of 0.2. +/- 0.2 provides large room for error; using a pH-KH-CO2 chart you may come up with 25 ppm CO2 while actually it is 10 ppm. By going high you increase the chances there is sufficient CO2.
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post #4 of 9 (permalink) Old 02-24-2005, 02:47 AM
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Rolo; You pretty much nailed it.

I was keeping my CO2 levels at a measured 25-30ppm for years and growth was so so. Notice that I said a measured 25-30ppm, who knows how actual it is. I cranked up the co2 to a measured 45-50 ppm and now my plants are growing like crazy, the fish are fine, no gasping. I don't know if its actually 50ppm but thats what the tests tell me.

The moral of the story is ,watch the plants and the fish, they'll tell you everything you need to know.

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post #5 of 9 (permalink) Old 02-24-2005, 03:14 AM
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My co2 levels tested, usually stay about 40-50ppm. I have yet to see any fish suffer from this. Growth is amazing. It's all about reading the plants and fish and not worrying about what the tests say. The tests are there for help.

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post #6 of 9 (permalink) Old 02-24-2005, 03:55 PM
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I am targetting for a CO2 in the 25-35 range. Recently, I had my CO2 shoot way up because I changed how my spray bar was pointing. I've read many other posts about folks stating that fish were hurt by high CO2 levels and were hanging out at the top of the tank. As I didn't see any change in the fish behavior (though, admittedly, being fairly new at this, I might not have seen the signs!) and things were busy, I didn't even notice the CO2 levels at 50-70 ppm for a couple of days. It took me several more days to even a week before I got the levels back down around 30.

So, are high levels of CO2 really that dangerous? Maybe it has to do with the species (though I have rummynose, cardinals and otos which I've heard can be fickle)?

Would love to increase my understanding on this item as well, so other experiences would be appreciated.

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post #7 of 9 (permalink) Old 02-24-2005, 04:32 PM
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I have read (I'm sorry I can't remember the book I read this in) that CO2 levels higher than 12 ppm can affect some fish species kidneys.
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post #8 of 9 (permalink) Old 02-24-2005, 04:57 PM
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Perhaps it is more of an issue of 1) pH and 2) stability. Can't say for sure though, just speculating.
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post #9 of 9 (permalink) Old 02-24-2005, 10:31 PM
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I only add CO2 during the day.

Chronic high levels can be potentially problematic for animals, bacteria fungi etc.

It also adds a measure of safety since all the CO2 degassess till the next morning.

So you only add CO2 for 10 hours basically.
Plants suck it up and grow like mad.

If my fish have any Kidney damage, I've never seen any evidence nor lost any fish due to CO2 yet. I've killed some shrimp though........

I added CO2 till got no longer got any positive response from the plants.
Beyond that level it becomes wasteful,and with CO2, can kill the fish.

But testing errors and light ballast and electrical current's influence on pH meters can cause issues.

Generally false positives(more CO2 than is really there).

EI is mainly for folks to get a handle on things or to whip the tank into shape for gardening. It assumes max uptake rates(this good advice if you do not know the aquarist tank's details to a large degree), you can back off the dosing of nutrients and see how the plants respond if you so chose. Generally CO2 is not something you want to back off of.

I have tanks I dose nothing to other than fish food also.

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