Hi all,
cheers Darrel
Up from about 300ppm pre-industrial revolution, and often higher in than 400 ppm in well insulated houses.Good old air pollution...increasing the concentration of atmospheric CO2
Probably not a formula, quite small trickle filters have the potential to deal with a lot of BOD, but in that case it is slightly different from CO2, as the wet surfaces in the filter contain the nitrifying bacteria and are using atmospheric oxygen. The CO2 they produce is out-gassed straight to the atmosphere.So taking that in to account along with a realistic carbon affinity for a hypothetically typical macrophyte, etc do you reckon it'd be possible to arrive at a rough formula for calculating trickle filter size?
Quite likely, and it doesn't have to be a soil substrate tank for this to happen, any tank with a high plant load is going to have CO2 levels build up at night, unless we take measures to out-gas it. This is actually another advantage as it stops your fish asphyxiating at night. The details for the dissolution of CO2 ar here: <http://www.pwtag.org/researchdocs/Used%20Ref%20docs/52%20Carbondioxide%20in%20water%20equilibrium.pdf>.Aside from that am I right in thinking water in equilibrium with air contains 0.5 mg/l CO2? If this is so, is it entirely possible - in soil substrate tanks at least with higher concs of CO2 due to decomposition - that trickle filters and tanks with large surface area:volume ratios are actually degassing CO2 to achieve equilibrium?
I think this is a pretty good summary of where we are. I also think you need to factor dKH into this as well, Diana Walstad is using a carbonate rich substrate because nitrification uses both O2 and carbonates.She also said that the CO2 amount produced is higher than the one via surface movement diffusion and that's what many folks don't understand. However she first advised to eliminate surface movement in order to prevent diffusion of CO2 in air, but she recently advised she's changed her mind, and advised for surface movement and means of oxygenation explaining that it's the oxygen those tanks are having problem with. It's way less solubale in water than CO2 but it's essential for decomposition of organics, so low oxygen, low CO2 at the end of the day. Without enough oxygen, there's not enough CO2 production, plants suffer, the substrate goes anaerobic, that leads to even less oxygen, bad bacteria flourishes, fish die
Yes that is really it, I'm not really interested in the levels of CO2 in my tanks, and I know that they will change dramatically during the photo-period, all I have to do is keep the oxygen levels high, have some nutrients (including CO2) and everything is OK.Oxygen is the key and I agree with Darrel on that as he pointed it out many times.
cheers Darrel