# good idea or crazy one co2 and o2?



## pyrrolin (Jan 11, 2012)

high co2 levels cause o2 to drop and fish to suffocate, so, what would happen if while diffusing co2 we also had another setup diffusing o2 at the same time?


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## Fishfur (Mar 4, 2012)

I'm curious, is that what actually happens ? Or does overdosing with CO2 simply make the levels too high for fish survival ? But I'll tell you what happened when I tried to get an O2 tank to use for fish.

I suspect that getting your hands on oxygen cylinders of manageable size may be impossible, unless you have a cooperative doctor or a good pal in the business of compressed gases. I wanted compressed oxygen to use with my tanks during pest control measures which were expected to last for a few days. So I wanted to seal the tanks securely from room air. But I feared a lack of air exchange or oxygen might kill the fish or shrimp.

I also feared that temperatures under the tightly sealed tanks would get too warm, further lowering oxygen levels. I wanted to pump in oxygen under the sealed wrapping, so I could keep the filters running and maintain gas exchange at the highest level possible, and it might possibly have cooled things off a bit too, since compressed gas is colder than room air.

I learned I needed an Rx for Oxygen. You can't just go get an oxygen tank like you can a CO2 tank. Unless you're a hospital, doctor or you've a legitimate industrial use for it, like a lfs might, for putting in fish bags, you're kind of SOL. The local Big Als has an oxygen tank, and it's enormous. If memory serves, four or five feet tall and extremely heavy, and I was told it costs a tidy fortune to refill when the time comes. [ don't recall how much $, but some hundreds ].

Can't imagine what putting them both in at once might accomplish, since once you hit the limit of the water's ability to hold a given gas, all the rest is going to the air. At any given temperature, water can hold just so much dissolved oxygen or carbon dioxide at normal air pressure.


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## BillD (Jun 5, 2006)

O2 doesn't dissolve as readily as CO2 in water. So, it would be easier to control the level of CO2 then to try and saturate the water with both gasses. An air stone would accomplish this. 
Those large bottles of oxygen, usually a dark red colour, are from a welding gas supply and don't require a prescription. They aren't meant for medical use, but are likely clean enough for fish bagging.


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## pyrrolin (Jan 11, 2012)

I was just thinking maybe it was a way to make co2 levels higher while keeping fish safe. You couldn't go too high with co2 but maybe much higher than normal.


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## jimmyjam (Nov 6, 2007)

o2 will increase if you have a good planted tank setup with proper dosing and co2 levels. My fish only suffers and I see them up at the top when my conditions are not properly set. This way there is less co2 uptake by the plants. Just keep a drop checker or ph monitor on at the right parameters and you will be fine. I would suggest dropping a airstone at night.


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## default (May 28, 2011)

Co2 and o2 saturation are different things, you can have high levels of both, you don't have to sacrifice or for the other - unless you're eliminating agitation to keep co2 which decreases o2... But the gases would not be competing for space.

The only time you need to worry about o2 is in the evening where the plants respirate co2 and require o2. But that can be easily solved with a air stone in the evening. However, if your tank is healthy with healthy plants, they should maintain your o2 levels for you, unless of course you're lightly stocked in plants (like one sword for a 90, some people don't understand what a planted tank is lol ) but if that's not the scenario, I wouldn't even bother increasing o2 during light hours.

Also, keeping pressurized o2 around the house is not the best idea, it's much more dangerous having it around heat/electricity than co2. I read Amano and other serious planters use o2 injection in their "masterpieces", but for most cases, it'd be a waste of time and money, just my opinion though.


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## LooseheadLen (Sep 27, 2014)

+1. I'm a newbie to planted tanks/aquaria but this is just straight chemistry.
O2 gas is extremely explosive. Assuming you saturate the water in the tank with O2, you'd need to seal the lid or at the very least, pipe in a "cap" of CO2 or N2 to prevent it escaping into the atmosphere and blowing up.
From a geek/tinker POV it'd be an interesting experiment but I don't think there's any benefit over plants and air stones and it'd be almost impossible to (reasonably) mitigate all the risks.


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## UnceasingStorm (Jul 16, 2014)

If you have a solenoid that shuts off CO2 at night I don't think you need to worry about gassing your fish. A dropchecker would help alot with knowing how much Co2 to get. I find that good circulation reduces the amount of Co2 you need to inject too (I went from 4bps, to 1bps after getting a circulation pump to get more water moving)


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