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Does C02 take away oxygen for the fish?

2K views 11 replies 8 participants last post by  flight50 
#1 ·
Does injecting CO2 take oxygen away for the fish or can the 2 chemicals coexist?

Do you need more oxygen to overcome the Co2 in the tank.

I never wanted to fool with C02 because I don't want to kill the fish in my aquarium but I have dwarf baby tears and I don't want them to die either.

Thanks.
 
#2 ·
In theory it is supposed to coexist but if it is pressurized, then we inject so much to make it into some kind of carbonic acid form that drops ph or something like that. Ya I know its complicated. Best thing to do - a drop checker. maintain yellowish green and your Dwarf baby tears and fish will be happy.
 
#6 ·
Yellowish and beyond is for a plant only tank. If you have fish or anything besides plants, your drop checker target should be a solid green. If its blue green or blue, you have low amounts of CO2. Green is considered ideal and the target for color for fish and plants to coexist with few issues.

To the OP, don't be afraid of CO2. If you research enough on here, you will see that a very large percent is using it or plans to in the future. Once your plants start responding as they never had before, you will be happy that you made the leap to co2. DIY will get your feet wet with co2 but a pressurized system is like going scuba diving, lol.
 
#3 ·
You are right, CO2 and O2 levels are independent of one another.

If there is good O2 level then critters can tolerate more CO2 though. So if you want to push CO2 to close to yellow in a calibrated drop checker you better have good circulation through the tank, a clear water surface and good ripple on that surface so there is as much O2 as possible in the water.
 
#5 ·
The levels of O2 and CO2 are independent of each other and maintain an equilibrium position in your tank having a fixed relationship as the atmospheric air. One will not drive out the other.

Most plants and fish are happy as long as the O2 and CO2 are at this equilibrium position. There are some fishes who like the water to have a little more O2, for example the hill-stream loaches. There are some plants which like the CO2 level to be higher like your baby-tears.

This equilibrium position does change; at night, or lights off period, the CO2 levels increase and oxygen levels decrease due to respiration of plants and fishes. During the lighted hours the opposite happens, due to photosynthetic activity of plants oxygen is given off and its levels increase and CO2 is absorbed by the plants so that its level falls. The diffusion of gasses through the water surface tries to equalise and offset the imbalanced equilibrium position, but this process of correction is low as the tank has a very limited surface area. Consequently a slight imbalanced position exists.

In planted aquariums, especially in well-lit tanks, most hobbyist add CO2 in one form or another to drive up the photosynthesis by plants and consequently the growth of plants, so that they over-compete with algae and keep them down. Most keep the CO2 level a little higher than the equilibrium position.

This higher CO2 level does have the effect of reducing the ph of the tank water. This drop in ph is in direct relation to amount of CO2 in excess of the equilibrium position. This drop in ph is due to the formation of H2CO3, a weak acid, too much of which will make your fishes gasp for air, even when the oxygen level is higher than equilibrium in the tank water.

The trick is to keep an eye on drop in ph of your tank, a drop checker (it checks the drop in ph level hence the name) and several electronic ph controllers are devices that helps you do that; although the most reliable method is to observe the fishes and and adjust the CO2 supply to a level they show no sign of distress. What you do is gradually, very slowly over days, increase the rate of CO2 supply (do that only when you have the time to observe and monitor the activity of the fish) and at the first sign of distress roll back the increase and fix it there.
 
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#8 ·
A drop checker is a drop checker. Its the solution you put in it that counts. Standard pH from a test kit such as API and a dH 4 solution of 2-4 drop to make a transparent / light blue solution is pretty much what you want to start with. I am not saying yellow will kill your fish but it is definitely on the higher end of your co2 limits. A solid green is the ideal target as I have mentioned. Greenish color of blue or yellow is under the ideal ppm range or over the ideal ppm range for CO2. If you are over the solid green and your pushing yellow or yellow - green, you will need to observe your fish. If you notice them swimming closer to the top, when they normally are mid or bottom swimmers, you will need to drop your bps.
 
#9 ·
I usually observe. I have Neon tetras and they are mid level swimmers if i am right. So as soon as I see them above a certain level, I drop down the CO2 but this has never happened to me after I dialed in initially. But the other thing I notice is, I have to dial in every time I change and clean the sponge on my intakes of the HOBs. I assume this is because of the amount of filtering and water surface agitation.
 
#12 ·
I assume this is because of the amount of filtering and water surface agitation.
The beneficial bacteria colony is disturbed. Not to much of an issue if the tank is healthy. They generate fairly quick. Just don't do a thorough cleaning of everything at once. That's asking for a re-cycle or potential crash. Your plants, substrate and pretty much any non smooth surface in your tank houses the bb. The filter is just a large percentage of the bb colony.
 
#10 ·
CO2 in the Tank

Hello mio...

If you're not using T5 lighting and don't have plants that require strong light, you don't need more CO2 than what's already in the air and that provided by the fish through respiration and their wastes. Separate CO2 systems are pricey and trickey to set up.

Most aquarium plants you pick up at the pet store will do fine in basic florescent lighting from the hardware store. I use either two or four fixture shop lights with T8, 6500K GE bulbs and keep the watts around 2 for every gallon of tank size. This level of light will grow most tank plants and the cost is minimal, around $40.00. The bulbs easily last a year.

B
 
#11 ·
Watts Per Gallon is no longer a thing in this hobby. T5, T8, T12, LED, Halides, CFL all produce different amounts of light.

Example: The same 100watt fixture that's 18 inches from your substrate could fry your plants and critters, requiring tons of ferts and CO2. But 30 inches from the substrate? You may never need to fertilize or use CO2.

PAR is what matters. Read about it here.
 
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