Near Fatal CO2 Overdose - The Planted Tank Forum
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post #1 of 3 (permalink) Old 02-19-2019, 03:02 PM Thread Starter
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Near Fatal CO2 Overdose

Hi folks,

On the weekend, I nearly killed off my tank because I neglected to keep an eye out on the CO2. By the time I realized things, I had loss one cardinal tetra, but the neon tetra was flopping upside down and not able to swim correctly. All my 2 bettas appeared fine although they still appeared a bit sluggish, but 1 was floating and not really moving much.

I quickly did a 40% water change, and put the fluval U2 filter in mode A which uses the air intake and aerates the tank quicker. The tetra disappeared and the next morning, I found him behind the filter, and I jiggled the filter off the glass and it swam freely! That was an amazing sight and serve me a reminder to be more mindful when dosing CO2. Just as well, my 1 betta recovered too.

It's a 8 gallon aquarium so need to watch it with a close eye to as if not overdose.

Just a lesson learn that I thought I'd share.

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post #2 of 3 (permalink) Old 02-19-2019, 04:49 PM
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Keep an eye out for any stress related illnesses that may occur due to this.
You see this a lot in fish in the aquarium; a stressful event lowers the immunity of the fish, opening them up to illnesses they would normally be able to combat when healthy.

Look for early warning signs:
Not eating
schooling/shoaling fish isolating from group

What you can do- even if do not see warning signs:
Keep water clean. Double water changes ( what you would normally do) for next couple weeks.
Vitamins- I use Boyds Vitachem.

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post #3 of 3 (permalink) Old 02-19-2019, 07:57 PM
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I've done the same but different method used! My 125 tank was full of African cichlids and I thought I understood the CO2 but then found a way to mess things up, even after several years. A larger tank is more forgiving and I am certain I would have lost the whole bunch on smaller but it is easy to make mistakes.
My mistake was a bit hard for me to figure until I went back to look carefully. I was moving tubing and simply left the CO2 running and let it all collect in the Grigg's style reactor while I moved and rearranged, then when I put it all back, the tubing and reactor had almost totally filled with CO2 and it went into the tank in one large gulp, rather than bubbled in slowly. Fish were upside down and backwards but they did all recover!
Even using a PH controller did not save me as the tank itself was still calling for more as the CO2 was collecting in the reactor!
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