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Question about non-CO2 injected tanks:

1125 Views 5 Replies 6 Participants Last post by  plantbrain

I am in the process of setting up a small (5g) planted tank. I will be running 13 watts of lighting and do NOT plan on using any CO2. From what I have read, when people run CO2 they try to avoid agitating the water surface since that accelerate the loss of CO2 from the water to the atmosphere (I think). My question is this:

In a non-CO2 infused tank, is it actually a GOOD idea to agitate the surface, maybe even add a airstone to actively aerate the water so that you can at least maintain normal CO2 levels in your water?

My reasoning is that, as the plants are actively photosynthesizing during the day, they will consume the dissolved CO2 in the water. I would imagine that, in a heavily planted tank without CO2, CO2 levels would progressively drop throughout the daylight period, perhaps even falling to levels that would prohibit, or greatly slow, further photosynthesis by your plants (as well as elevating pH). By actively agitating the surface, and by adding an airstone, you would be replacing the lost CO2 much more rapidly than by simply waiting for the passive diffusion of CO2 from the atmostphere into the water.

Any opinions? Anyone tried to do this with positive or negative results? I was planning on dumping an airstone into my filter compartment and blasting the water on its return to the tank.

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You are correct, agitating the surface is good, although you won't be seeing the plants photosynthesize.
With a decent fauna load and food you will be providing a little N & P.
So once a week you will want to dose a little K+ & Trace.
I'm not sure about agitating the water surface. Dissolve CO2 is pretty volatile. Think shaking a can of soda. I have a small powerhead under the surface to circulate the water.
i have a 5.5 with 13w cf, no co2, no excel.

i have a spraybar from my tom's rapid filter pointed at the surface and a plain airtube bubbling gently in the opposite corner.

hygrophila polysperma, h. corymbosa, java fern/moss, cryptocoryne wendtii, and echinodorus tellenus grow slowly but nicely. 5 cardinals, bunch of shrimp.

rarely add ferts, no water change for months at a time, just top off, scrape gsa from glass when it gets really bad. easy, low maintenance. looks better than my high maintenance, high light, co2 injected 20 gal.
It may depend on your fish load too. Fish produce co2.
I use less flow on my non CO2, still, they get decent flow, adding more does not appear to help though near as I can tell.

Some seem to believe they can add enough CO2 via aeration to keep the CO2 at 0.5ppm(ambient based on partial pressure). That's not much to begin with. Some will build up slowly over night time. You might have 2-4ppm in some tanks, fish give it off at night(a little, but not that much) and it can accumulate.

So in the first 1-2 hours, plants have a fair amount of CO2.
If you have lots of aeration, the CO2 is less at that point.

So you end up with less plant growth. After 1-2 hours, the CO2 is back down to 0.5 or less and limits the algae and plants' growth.

So you get a nice little spurt of growth in the morning if you do not over do the aeration and filter flow.

Fish cannot supply much CO2 during the day nor will aeration after the lights have been on for 1-2 hours though.

If it did, we'd just do that instead of adding CO2 gas:thumbsup:

Tom Barr
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