CO2 verse O2

[spiketooth]

Ok either this makes no sense or I am on to something, so co2 changes your ph depending on the amount of co2 your putting in the tank. At one point the ph will be stable but at night time plants stop using co2 but the fish are still producing co2. With no air stone co2 is going to continue to build up. With a airstone it help removes co2 and provide more o2 with surface agitation, which once again would change your ph a little depending on the amount of bubbles and surface agitation . End theory if I turn co2 off at night but turn on air stone to a low setting I should be able to get a balance between co2 and o2 during the day and night to keep my ph stable. How does this sound??????

 

[maxwellag]

Most people who use co2 turn it off at night (if possible, DIY co2 is usually too simple to do this with) for that same reason. Even after the lights have turned off, plants continue to use co2 and produce o2. There is still a minor PH swing, but it is nothing that can do much harm. An airstone will help reduce the amount of co2, but with plants in your tank, the co2 should get used up pretty quickly anyway. I never have airstones in my tanks for this reason.

 

[aqua_chem]

First off, DIY or pressurized?

Second, O2 isn't really a concern with pH.

Third, pH isn't really a concern in my mind at all. CO2 levels will affect fish though, so your concerns aren't necessarily misplaced.

Finally, DIY co2 can be hazardous, especially in smaller tanks where relatively small amounts of co2 can build larger concentrations. Larger tanks, especially ones with adequate filtration and surface agitation, shouldn't build up higher levels of co2, especially at night.

 

[yee.simon]

Hi
I put everything on a timer for the tank when running co2, fans (cooling), lights / air pump alternating period on the day. At night only air pump turns on. With a HOB I have additional turbulence for oxygen circulation. With the co2 indicator turning green means the plants are getting enough co2 blue is not sufficient, yellow is to high. But I was told to have a balance between of air pump/turbulence and co2. I think selection of plants and fish is also important. Any ideas what plant fast use up co2 fast and consume a lot lights?
Thanks

 

[aqua_chem]

Any plant that grows fast will use a lot of CO2. That being said, I think using plants to balance out CO2 absorption is probably a futile idea, as you can't measure it, can barely control it, it's probably an extremely small contribution, and the alternative methods are all extremely efficient.

 

[yee.simon]

Hi
Maybe should shorten the time?

 

[spiketooth]

If you measure your ph and kh they have a chart to tell how much co2 is in your water. I am always in the low amount so I don't have enough co2 in my water on top of that if I put to much co2 in the water my ph will change. I am just trying to get a happy balance between co2 and o2

 

[phin]

Most people who use co2 turn it off at night (if possible, DIY co2 is usually too simple to do this with) for that same reason. Even after the lights have turned off, plants continue to use co2 and produce o2. There is still a minor PH swing, but it is nothing that can do much harm. An airstone will help reduce the amount of co2, but with plants in your tank, the co2 should get used up pretty quickly anyway. I never have airstones in my tanks for this reason.

maybe you misspoke?

Plants photosynthesize during photoperiods. Simply put: carbon dioxide + water + light = sugar + oxygen. Without light there is no photosynthsis.*

*The Calvin Cycle is independent of light, but does not produce O2.

During the non-photoperiod (when no photosynthsis is going on) plants use oxygen and put out CO2 in a process known as cellular respiration. Which is basically the opposite of photosynthesis: sugar + oxygen = energy + carbon dioxide + water.

 

[yee.simon]

maybe you misspoke?

Plants photosynthesize during photoperiods. Simply put: carbon dioxide + water + light = sugar + oxygen. Without light there is no photosynthsis.*

*The Calvin Cycle is independent of light, but does not produce O2.

During the non-photoperiod (when no photosynthsis is going on) plants use oxygen and put out CO2 in a process known as cellular respiration. Which is basically the opposite of photosynthesis: sugar + oxygen = energy + carbon dioxide + water.

Ok I understand that now

 

[maxwellag]

maybe you misspoke?

Plants photosynthesize during photoperiods. Simply put: carbon dioxide + water + light = sugar + oxygen. Without light there is no photosynthsis.*

*The Calvin Cycle is independent of light, but does not produce O2.

During the non-photoperiod (when no photosynthsis is going on) plants use oxygen and put out CO2 in a process known as cellular respiration. Which is basically the opposite of photosynthesis: sugar + oxygen = energy + carbon dioxide + water.

Yes, I meant that. Lol I got distracted and then tried to keep typing from memory. Didn't work so well...

 

[spiketooth]

What I said makes a little sense then, plants produce co2 at night. Which then effects the ph by( I looked this up) co2+h20=h2co3 then this carbonic acid reacts slightly and reversibly in water form a hydronium cation, h3o+, and the bicarbonate ion, HCO^3-. In other words lowering the ph. If I want to increase the amount of co2 during the day to provide enough for my plants I would turn it off at night and turn on a air stone to keep a stable ph. My ph from 7.4 to around 6.8 with co2 I will measure my ph before I turn on the light but I am going to guess its going to be around 6.6. Ok this didn't hit me until I typed it lol. If my reading is at 6.6 in the morning then I turn on co2 bring it back to 6.8 because of the plant photosynthesis, then I would not need a air stone because that's just a .2 change. Just have to make sure I turn on the co2. Thanks for the help everyone lol. Or I may have confused myself even more HA

 

[phin]

What I said makes a little sense then, plants produce co2 at night. Which then effects the ph by( I looked this up) co2+h20=h2co3 then this carbonic acid reacts slightly and reversibly in water form a hydronium cation, h3o+, and the bicarbonate ion, HCO^3-. In other words lowering the ph. If I want to increase the amount of co2 during the day to provide enough for my plants I would turn it off at night and turn on a air stone to keep a stable ph. My ph from 7.4 to around 6.8 with co2 I will measure my ph before I turn on the light but I am going to guess its going to be around 6.6. Ok this didn't hit me until I typed it lol. If my reading is at 6.6 in the morning then I turn on co2 bring it back to 6.8 because of the plant photosynthesis, then I would not need a air stone because that's just a .2 change. Just have to make sure I turn on the co2. Thanks for the help everyone lol. Or I may have confused myself even more HA

I think a lot of your method depends on how much CO2 is being injected during the day relative to the amount of CO2 consumed by the plants during photosynthsis and your bicarbonate buffer level. The CO2 generated by the plants during respiration will be less than the CO2 injected during the day if more CO2 is injected than is being consumed. In this case, a net decrease in CO2 will result in a decrease in carbonic acid and bicarbonate, resulting in an increase in pH at night.

With an adequate bicarbonate buffer level and CO2 injected at a rate at which it can be fully consumed you can avoid a pH increase at night when the CO2 is turned off. Likewise, you can avoid a pH decrease when CO2 is injected during the photoperiod by the same principle.

So, to summarize, an adequate KH level will guard against pH swings with the change in CO2 concentration.

 

[spiketooth]

Theres part of the little problem for me, ny kh is around 1.5. Been like that for the past 3 months

 

[phin]

What size is your tank? You can increase your KH with carbonate, try baking soda (sodium bicarbonate) or potassium bicarbonate. You may be able to find potassium bicarbonate at a machigwa from a vendor who sells brewery ingredients.

 

[spiketooth]

Not going to mess with it, its stable and the fish are happy. Plants are growing. Dont want to put things out of wack, its a 75 gal planted tank( about 30 plants)

 

[phin]

I understand what you are saying - stability is key. However, I don't think there is much disagreement that KH should be at least 3 degrees. 3-6 dKH is optimal. It will help to keep your pH stable in the future and guard against pH drops. I would be wary with CO2 injection and 1.5KH. If you don't want to buffer the water anymore then keep a very close eye on your pH.

 

[spiketooth]

Will do, thanks

 

[phin]

on your 75 gallon tank. just add a teaspoon of baking soda once a day and measure KH, until your KH reaches the desired amount. It won't take much, but doing just 1tsp/day will me a very minimal change daily.