Co2...24/7 or not?

[jmarsh3253]

I have a 55G rather heavily planted tank for Discus. My pH is 7.5, KH is 10-12 degrees...175-210PPM. Should I run the Co2 24/7, or in conjunction with my lighting...on at 9:00am, off at 8:00 pm? Which causes the smallest variation in pH overnight? I want to try to keep it as stable as possible for the Discus. Additionally, I have my Rena canister's spray bar on the back glass, pointed down to minimize surface turbulence so not to off gas the Co2. Will there still be enough water movement for oxygenation...I also have a HOB Aquaclear 50? Thanks for your help.

[nickmcmechan]

if the surface turbulence is low then the CO2 will be effective

i run mine 24/7

if overnight running is too much you'll soon see the fish hanging near the surface for air

this website will help you measure it, i suggest first thing in the morning to see what level you have overnight: http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

if you are worried about it then run an airsotne on a timer to run during hours of darkness

[125gJoe]

..Just my opinion, and what I have learned from this website over time...

CO2 injection should be turned OFF at night.

The plants can't utilize the CO2 at night, and it gasses off at night. CO2 at night is a waste of CO2.

A simple, cheap timer can be used to regulate the proper amount.

DIY CO2 is another story....



___________

[Ralleh]

If you are turning it on and off, you will get wild pH swings.

[180gz71]

If you are turning it on and off, you will get wild pH swings.
This is very true. The ph is directly affected by co2. You will have less of a swing in ph( which the fish are more affected by than co2) if you leave the co2, and run an airstone at night to keep the tank well oxygenated. This is what Ive been doing with my 180 gallon for over a year now, and not a single fish has been seen gasping at the surface.

[Sammie7]

Changes in Ph caused by CO2 injection does not harm the fish.
http://www.aquariacentral.com/forums/showpost.php?p=815765&postcount=2

Turn off the CO2 at night, because otherwise you are just wasting it.

[star_rider]

the pH swing relative to co2 is not harmful to the fish..the gh does not swing the difference is the carbonic acid created from the co2..the drop in ph is related to the rise in carbonic acid..when you turn the co2 off at night the carbonic acid also drops and the pH rises.

the kH and Gh are not affected. the water is is still stable.(relative to having the proper kH which should at least be 3-4 degrees.

you will have more issues with pH if you have low kH and the ph is not stable.in this case the pH will swing due to the lack of stability and this is harmful for the fish.

I agree..turn the CO2 off at night and save it for the day.

[nickmcmechan]

i would say that if its diy co2 run an airstone at night, if its pressurised turn it off at night...you'l save some cash as well!

[maxthedog123]

I think turning it off at night is another one of those things that becomes accepted wisdom that really isn't right. I leave my CO2 on 24x7 and it works great. My pH is about 6.6 in the morning and about 7.0 at night. With a KH of 4ish, that is nearly spot on 30ppm CO2 in the morning - a PERFECTLY safe level for the fish.

One of the best discussions on the topic - I have posted this before.

http://www.thekrib.com/Plants/CO2/night.html

[180gz71]

Well, all I can comment with is from my personal knowledge( and it is quite possible that I could be wrong) and since Ive been running pressurized co2 I have always left it running. I also use a ph controller with no issues. I have had this setup going on 3yrs now. I personally believe that the tank parameters will stay more stable by leaving the co2 running all night, whether it be ph swings or oxygen levels. I also bought a 50lb co2 tank, so maybe I dont have to worry so much about wasting it. Although, there are many aquarists who do turn it off at night with great success. This is just my way and it works also.

yeeha,
mark

[BradE]

If you are turning it on and off, you will get wild pH swings.

I have to disagree with the above statement.

In my planted 55G (4 watts/gal, pressurized CO2, pH 6.8-7.0; GH 7; KH3) my pH only changes about 0.2 points from day (CO2 on) to night (CO2 off).

[180gz71]

I have to disagree with the above statement.

In my planted 55G (4 watts/gal, pressurized CO2, pH 6.8-7.0; GH 7; KH3) my pH only changes about 0.2 points from day (CO2 on) to night (CO2 off).
Just a quick question, is that with a test kit or a ph controller/monitor?

[Slappy*McFish]

What a lot of people refer to as pH shock is actually osmotic shock. That's why CO2 pH swings aren't harmful but KH(baking soda) and TDS induced pH swings are. It's the osmotic pressure change that kills the fish.

[plantbrain]

I think the strongest argument in favor of turning CO2 off at night is fish health.

While we cannot vary NO3, PO4, NH4 etc, we can rapidly change the CO2.

Does anyone here believe (honestly) that 1 ppm of CO2 is worst, than 30ppm of CO2 to fish?

CO2 is a "pollutant" and a toxin, much more so than NO3(but not even close to that of NH4), yet we add it without issue.

Some bicker about higher NO3 levels however even though CO2 is the cause of far more fish death, no one has killed their fish using KNO3 to date that I've heard of.

Fish use a lot of energy to respire.
This is a two edge sword, why?

Fish respire CO2 and take up O2.

It's not just about O2 alone nor CO2 alone.
It's both.

When we have the day light and high CO2, that's fine because the plants are producing a lot of O2.

At night?

No!
So towards the dawn, you have the lowest O2 levels and the highest CO2 if you use 24/7.

This is radically more important than pH swings which have no bearing on fish health in terms of CO2 enrichment. If so, we could not do massive water changes without adding CO2 back to the replacement water...........which almost no one does. Folks have been doing large water changes on planted tanks for many decades and use CO2 also, so clearly my fish are not dead, so I have a hard time accepting the notion that pH swings due solely to CO2 are any concerned for fish, you need to prove decades and 1000's of tank's worth of observations to explain that one away!

Which clearly folks are not going to be able to do.

So..........we are left with that it does not matter nor help.
It's(24/7) a simpler method for many folks, and if you do not add enough or have a lower flow tank, then perhaps you need to have a full CO2 enrichment when the lights come on to start with, but if you focus on adding a more responsive CO2 system to begin with, there's no need.

Fish do not do as good with high CO2 and lower O2.
They do okay with high CO2/highO2.
They do well with high O2 and low CO2.

So it's two things.
If you have issues adding CO2:

Add more surface movement, enough to see the water moving but not enough to break the surface.

Will you lose some CO2?
Yes.
But it's cheap and adding more is simple, turn the knob another 1/4 turn:grinyes:
What do you gain?

Well, more O2 at night when you need it.
Better circulation/more flow.

Better bacteria conversion of waste(they use O2 as well).
Clearer tank.

You can also help by having plenty of good current in the tank as well as having lots of flow through CO2 reactor(more is better until you start degassing the unit). Or good flow by a disc so that the mist gets well distributed throughout the entire tank.

A pH/KH drop checker can also help a great deal and makes monitoring CO2 much easier.
http://www.barrreport.com/estimative-index/2818-drop-checkers-co2-indicators-why-how.html
I like CO2 mist methods which you can check here:

http://www.barrreport.com/co2-aquatic-plant-fertilization/2983-future-notes-co2-mist-methods.html?highlight=CO2+mist

Basically blasting CO2 mist before it can fully dissolve into the plant beds.
Gas froth CO2 essentially.

As the plants grow and fill in, the flow and current dropos dramatically, by about 3-10X. you need to either add more current or kept the plants well pruned, slower growth, (less light etc will do that), chose slower growing species etc, or prune a lot more.

All these things influence CO2, O2 and fish health.

They are interwoven so while you might want to isolate things, you will also want to consider what else might be happening.

Regards,
Tom Barr