C02 Levels & Plants

[mark4785]

I'm completely new to planted aquariums and was curious as to whether a certain c02 level (while possibly good for the plants) can cause fish to suffocate?

I've been looking into the Redfield Ratio and it suggests out of Phosphate and Nitrate, C02 is most essential. Should I really follow this ratio given that I have a lot of fish that need a lot of oxygen rather than c02?

If there is a certain c02 level that must be avoided for the safety of the fish, would it be worth me investing in a c02 indicator?

Mark.

 

[mtv8dmarine]

I personally don't use CO2 due to my lighting but I believe those that use CO2 disperse it during the day while the plants are photosynthesizing. During this period, the plants are absorbing CO2 and water. The plants produce glucose which it stores as a food source and releases oxygen as a waste product. However this process only occurs while the lights are on.

A process that never stops is the plants' respiration. The plants consume the glucose it produces and oxygen which provides the plants the energy to grow and heal. This also means that CO2 is an expelled waste product.

Since respiration never stops and photosynthesis does, you can see how there's a CO2 buildup at night and why CO2 subscribers only dose during the day.

As far as the dosing requirements I can't help you there.

 

[RadaR]

Please dont take the Redfield Ratio literally. It's old and confuses/misleads folks. If I remember correctly it was actually formulated for marine algae. It talks about ratios when infact plants couldnt give a monkey what ratios you deleiverd the nutrients in so long as there was enough of the nutrient. Loads of tanks do not follow these ratios, just make sure that nutrients are not a limiting factor.
To measure CO2, see this guide. It will explain everything.

 

[mark4785]

I personally don't use CO2 due to my lighting but I believe those that use CO2 disperse it during the day while the plants are photosynthesizing. During this period, the plants are absorbing CO2 and water. The plants produce glucose which it stores as a food source and releases oxygen as a waste product. However this process only occurs while the lights are on.

A process that never stops is the plants' respiration. The plants consume the glucose it produces and oxygen which provides the plants the energy to grow and heal. This also means that CO2 is an expelled waste product.

Since respiration never stops and photosynthesis does, you can see how there's a CO2 buildup at night and why CO2 subscribers only dose during the day.

As far as the dosing requirements I can't help you there.

Hi, thanks for the response.

During the day, the aquarium is in a room with the blinds closed so it's very dull in the room, almost resembling night time. Given this, will the plants be absorbing oxygen during the day given the conditions? I turn my aquarium lights on at 7pm which should then prompt photosynthesis, in which case 7pm or later would be the best time to dose c02?

 

[mtv8dmarine]

Yeah in that case you would dose CO2 during the time the lights are on since that triggers the photosynthsis period. You are keeping your lights on for 8 hours though right? Not until like 7 the next morning because that would be too long.

 

[mark4785]

Yeah in that case you would dose CO2 during the time the lights are on since that triggers the photosynthsis period. You are keeping your lights on for 8 hours though right? Not until like 7 the next morning because that would be too long.

The lights turn on at 7pm and go off at around 12:30am. I've been told to leave them on no longer than 6 hours as, presumably, by the 6th hour, the plants will have got enough nutrients and therefore any left over nutrients will start to feed algae.

 

[ian]

If you're dosing liquid carbon ie Easycarbo/flourish excel, it can be dosed anytime within 24hrs. It has a 24hr half life, so can be dosed when the lights are on or off.

 

[RadaR]

Yeah in that case you would dose CO2 during the time the lights are on since that triggers the photosynthsis period. You are keeping your lights on for 8 hours though right? Not until like 7 the next morning because that would be too long.

the plants will have got enough nutrients and therefore any left over nutrients will start to feed algae.

Doesnt work like that I'm afriad.

 

[mark4785]

So if I was to use c02 in my sparcely planted tank, dosing it when the tank lights are on is the most safest time to do it?

I think this question is extra important because in an effort to raise c02 levels yesterday, I turned my airstone off as I was told water ripples would produce enough introduction of oxygen (for the fish) and c02 (for the plants), but 24 hours after turning it off one fish has died (Dwarf Neon Tetra) and others of the same species were gasping at the surface (this is WITHOUT introduction of liquid c02!) so I'd hate to think what the inhabitants would look like if I had dosed c02 AND turned the airstone off..

I've turned the airstone back on on the advise of a LFS owner who said it encourages and abundance of oxygen and improves water circulation (contradicting a FF user) and is stating liquid c02 isn't necessary (again, a contradiction) in a tank with not many plants.

 

[mtv8dmarine]

If you are dosing gas CO2 than you only should be doing it during the photosynthesis period. If you are dosing liquid carbon products, then they can be dosed day or night.

In planted tanks, bubblers exchange too much oxygen for CO2. Which of course you have identified as a more oxygenated environment for your fish. We don't run bubblers because they are unnecessary. All that is really needed is the water surface being rippled which promotes oxygenation in itself without the heavy exchange from tank bottom to tank surface. You do need to have enough surface agitation though. This can be done by using your power filter is you have one and allow it to cascade into the tank instead of the out-spouts already being below the water surface.

Many things govern whether CO2 injection is necessary or not. I have a moderate to heavy planted planted tank with no injection. Why? Because light wattage per gallon is the factor. I'm running about 1 watt per gallon. This means my plants are low light and slower growing plants. I don't need CO2 injected. I can get away with dosed carbon. Now that's not to say CO2 wouldn't be beneficial. However, if you're running something other than a low wattage tank, then CO2 injected becomes more of a requirement.

Here's a video I just took of my tank to show you my fish aren't needing a bubbler. They all swim from bottom to top and really only surface to eat and play in the stream of forced water on the right side. My corydoras never breach the surface and always stay submerged which tells me there's enough oxygen.

Pardon the background static and poor video quality. The mic is way too sensitive because I have no idea what ambient noise it was picking up and amplifying like that.

http/www.youtube.com/watch?v=JiYdr9tWcog

Also what's sparsely planted? Can you give us some info on your tank, light wattage, and how many plants you have?

 

[PDSimon]

Totally agree with the above post, I have even less surface agitation than that and all my fish are in good condition.

I think also neons are generally for mature, 6 month+ tanks so you could put it down to that.

 

[mark4785]

If you are dosing gas CO2 than you only should be doing it during the photosynthesis period. If you are dosing liquid carbon products, then they can be dosed day or night.

In planted tanks, bubblers exchange too much oxygen for CO2. Which of course you have identified as a more oxygenated environment for your fish. We don't run bubblers because they are unnecessary. All that is really needed is the water surface being rippled which promotes oxygenation in itself without the heavy exchange from tank bottom to tank surface. You do need to have enough surface agitation though. This can be done by using your power filter is you have one and allow it to cascade into the tank instead of the out-spouts already being below the water surface.

Many things govern whether CO2 injection is necessary or not. I have a moderate to heavy planted planted tank with no injection. Why? Because light wattage per gallon is the factor. I'm running about 1 watt per gallon. This means my plants are low light and slower growing plants. I don't need CO2 injected. I can get away with dosed carbon. Now that's not to say CO2 wouldn't be beneficial. However, if you're running something other than a low wattage tank, then CO2 injected becomes more of a requirement.

Here's a video I just took of my tank to show you my fish aren't needing a bubbler. They all swim from bottom to top and really only surface to eat and play in the stream of forced water on the right side. My corydoras never breach the surface and always stay submerged which tells me there's enough oxygen.

Pardon the background static and poor video quality. The mic is way too sensitive because I have no idea what ambient noise it was picking up and amplifying like that.

http/www.youtube.com/watch?v=JiYdr9tWcog

Also what's sparsely planted? Can you give us some info on your tank, light wattage, and how many plants you have?

Hey,

Well the tank has 120 litres of water, 2 x 24W T5 bulbs and it contains 1 x Elodea densa, 1 x Cryptocoryne and 1 x Anubias.

The Youtube videos linked below, show the ripple effect of the water; please tell me what you think of it because I really don't know what amount of surface movement equates to enough oxygen for 5 Black Neon Tetra, 4 Dwarf Neon Rainbowfish and 2 German Blue Rams. Video 2 shows a male Dwarf Neon Rainbowfish gasping at the surface even despite the airstone being switched on and ripples being apparent.

1. Click here for video 1.
2. Click here for video 2.

Mark.

 

[PDSimon]

Have you checked your ammonia, nitrite and pH?

 

[mark4785]

Have you checked your ammonia, nitrite and pH?

Just completed a water test and ammonia is 0, nitrite is 0 and PH is about 7.4.

If I felt any of these parameters were getting a bit excessive I wouldn't have the tank stocked at this point.

Why do you ask?

 

[mtv8dmarine]

You do only have a few small plants in the tank which aren't by themselves going to produce a whole lot of oxygen for the fish. A good way to tell if your fish are receiving sufficient O2 in the water is to watch and see if they go to the surface for air or if they stay submerged and breath there. If your fish are not surfacing then there is enough. If you turn off your bubbler for 20 minutes and watch your fish this will tell you if the rippling as it is provides enough surface agitation.