CO2 , dawn and dusk

[Pete Quince]

Hi. Im setting up a new 200l aquarium, and am looking at installing a pressurised CO2 system. I have read that i should use a plug in timer, to power my solonoid valve on the regulator. The advice i have gained says to start CO2 injection 1 to 2 hours before the lights come on in the aquarium, and cease injection 1 hour before the lights turn off. My query is this.. As my light system has a dawn/dusk light effect.....is my aquarium considered to be lit when the faint blue light is on, replicating daybreak..or when the lighting has reached a high level of brighter light. Again is my light system deemed off, when the light begins to fade, replicating sundown, or when the light turns off fully. I guess im wondering if a light buildup will allow my plants to absorb CO2 enough, through photosynthesis, to negate a risk of CO2 poisoning of my fish, either before the light gets from a low to a high brightness, and later from a high to a low brightness. Does this make any sense.

 

[John q]

. I guess im wondering if a light buildup will allow my plants to absorb CO2 enough, through photosynthesis, to negate a risk of CO2 poisoning.

If the CO2 is tuned correctly the lights coming on, or off shouldn't significantly (+/- 0.1 in ph terms) alter anything . If it does then one needs to re tweak the settings, especially if "poisoning" is in the back of your mind.
Also worth mentioning that the CO2 can be turned off about an hour before the lights go off.

 

[PARAGUAY]

You can also run a airstone at CO2 off period

 

[foxfish]

Hi Pete, welcome to the forum, I can understand why you have asked your question, there could be a few in depth answers.
However let’s start by asking how long is your brighting up period ?
To simplify the situation you could make this period as quick as possible, say over 10 minutes then you wont really have any issues to worry about.
What we are trying to achieve, is to offer the plants enough C02 to help them grow as soon as the lights are bright enough to allow photosynthesis.
Of course there is more to supplying just the right amount of C02 and you can find hundreds of post explaining about how to do a PH profile.

 

[bazz]

As my light system has a dawn/dusk light effect.....is my aquarium considered to be lit when the faint blue light is on, replicating daybreak..or when the lighting has reached a high level of brighter light

To simplify the situation you could make this period as quick as possible, say over 10 minutes then you wont really have any issues to worry about.

Again is my light system deemed off, when the light begins to fade, replicating sundown, or when the light turns off fully.

This is what I do a 10 minute start up and then later a 45 minute wind down to have some early evening aesthetics.
What @PARAGUAY mentions above will alleviate the problem, I think my use of a surface skimmer intake assists in degassing having a similar effect.
As @John q states 'Also worth mentioning that the CO2 can be turned off about an hour before the lights go off.' From what I've come to learn, plant's metabolism slow down later in the day and therefore photosynthesise less towards the end of the photoperiod thus using much less CO2.
Cheers!

 

[Pete Quince]

ok, Thanks All. Now a further question. When the solonoid is fitted to a socket mounted timer, when the solonoid is powered, is it on or off...ie if the power kick on, does it open the Valve to allow co2 into the tank, or does it close it. Reason is can the solonoid valve and a air pump be connected to the same timer, so that when the solonoid closes, and CO 2 ceases, the air pump turns on, and pumps air into the tank. I know i could put a seperate timer on each module, but just wondered.

 

[bazz]

When the solenoid is powered it is on or open. A 4 way smart power strip Amazon product ASIN B07NXSTQV8 or similar alleviates the problem.