Co2 and something to think about

[got_nailed]

I will try to keep up with this post every few days.



Most of the “gas off” of Co2 happens at the water surface. If you can keep a high level of Co2 between the top of the water and the under side glass top, then in theory you can keep your tank at a higher Co2 PPM using less Co2.

I have been keeping one of my 75 gallon planted tanks between 28 to 38 PPM with 2 2letter DYI Co2 for about 3 months now (all fish have been removed). I’m pumping the Co2 in to the space between the water surface and the glass top. I have dropped the water surface about 2 inches causing my canister filters to splash a lot of water (normally there would be a higher level of O2 in this air).

All I did to modify my glass top was get some extra black “hinge” and to cut some acrylic to replace the flimsy plastic material. I drilled the all the holes going though (2 air hoses Co2, 4 holes for canister filters. I did use a little silicon to make this part air tight). This will seal up most of the air gaps in the lid once some water gets one to the lid shelf and into the hinges.

The down side of doing this is having to deal with the acrylic with fixed tubes in it. You can just fold the 3 part top over, or just pull the hinge apart.

 

[happychem]

Interesting concept. It sounds like your tank is more or less hermetically sealed. If so, thermodynamics is against you in the long run, but the gas and water exchange during your weekly partials might be enough to restore the energy lost. I'm interested to see how this turns out.

 

[zkt]

Sounds good to me ! Lot of surface area in contact with th co2. Wouldnt have to be airtight- just a dead air (co2) space. The co2 being heavier than air would tent to blanket the water sirface. Just have to keep it from being blown away.

 

[happychem]

Actually, the surface area is very small. Only the surface area of the tank plus a little from the waves formed in the surface distruption.

 

[zkt]

rite! I was comparing it to the surface area of small bubbles rising thru the water tho.

 

[happychem]

Yeah, those have a much larger surface area per unit volume.

Consider the current experiment: the gas volume is in roughly the shape of a rectangular based prism. The only contact area is the base.

Now take that same volume and turn it into tiny bubbles. The surface area to volume ratio increases exponentially. In other words, the gas "sees" more water, which increases the amount of time required for the gas to equilibrate with the water.

 

[zkt]

Carry that reasoning even further and and decrease the bubble size to a point and the surface area becomes infinity. Since the smallest co2 bubble size attainable is a molecule, if follows that the best way to mix gas and water is when they are both a gas, Which we knew in the first place.

 

[zkt]

Now ya for be thinking about this. Picture this : a sealed space above the water filled with co2. The water evaporates from the surface of the tank, mixes with the co2 and forms carbonic acid gas. Blow it around with a cpu fan.
Place a Peltier junction, cold side down, in the space. Carbonic acid condenses on it and falls into the tank.

 

[RTR]

Isn't it easier just to dissolve the gas in the first place in a reactor?

 

[Mrditty]

Or you could really go of the deep end and place on of those fogger thing amighigys in a container run a water line from the tank into it and one from the cantainer back to the tank run your co2 line into it then seal the canister up air tight turn it on.

Or how about devising a way to use dry ice and hey you could do away with the cillers in the summer to.

who knows seems like to much work to me.

I have to say I have been useing a single ceramic disk in my 160 for 8 months now with great results. And a 20 gallon tank last me for a year.