I have 4 questions for you:
1. How do you measure precisely Co2 concentration? In your Co2 article you mentioned the KH/ph correlation, but how you calculate that?
a) I measure the pH, alkalinity and temperature (sometimes myself, sometimes in the lab), and based on these data I calculate the CO2 concentration using the
CO2 calculator on my site.
b) I use a dropchecker to check if I am somewhere near to the calculated numbers.
I don't have a CO2 meter, yet I believe that the calculated data are quite close to the real values in my tank.
2. What about flow? What's your opinion on water flow and how that can affect plants as well as Co2 distribution and stability? What's your recommended water flow compared to tank size?
Flow is quite important in my opinion, as for all the nutrients (incl. CO2) to get into our plants they need to overcome some bariers => boundary layer, cuticle, cell membranes etc. The bigger the boundary layer or the thicker the cuticle, the slower is the diffusion of nutrients into the plant leaves. And flow can substantially reduce the thickness of the boundary layer. So in the tank with a good flow, the nutrient uptake by plants is much faster (more effective) than in tanks with slow or no flow. As to my recommendation, I think that the flow should be as fast as possible, BUT not as fast so that the plants won't be able to keep their leaves in a proper position toward the light source (in other words, plant leaves need to be directed toward the sun, so if the flow is too strong and the leaves are ripped by the current, that's already too much. So higher flow means usually better nutient uptake rates.
3. Always in your Co2 article, you found out that to have stable Co2, we need aeration via surface rippling or other similar way, but what if the surface rippling is to much? Can that cause a disruption of Co2 stability and create a negative effect?
I think that too much surface rippling won't lead to CO2 unstability but rather to lower yet stable CO2 levels. The more rippling, the more degassing will take place. If you add CO2 into your tank, its concentration will
constantly increase under normal conditions (why? because the amount we usually add into our tanks is quite big, and the degassing rate is too slow to compensate it). So if you add (say) 4 bubbles per second into 60L tank, the CO2 concentration may rise up to 80 ppm. And the CO2 concentration will keep increasing until you turn the CO2 supply off (and the evening). Then it will began to
slowly decrease. In case you add rippling into this equation, the CO2 will degass much faster, but the result won't be fluctuating CO2 levels but rather perfectly stable CO2 levels. The CO2 will degass in a constant rate, so as soon as the CO2 level reaches some equilibrium point (say) 25 ppm, it won't increase any further but rather stays the same for the whole day. All this is clearly visible in
my charts. So by rippling you definitely lose some CO2 from water, but in exchange for it you'll gain much stable levels. BTW, if you use wet/dry filter you probably don't need surface rippling as this kind of filter would have probably same effect on the degassing as rippling.
4. Back to BBA, do you think Co2 fluctuations could really contribute to BBA, and maybe flow, degassing and rippling could play a role in that?
I can't imagine such CO2 fluctuations which may play some role in algae infestations. I believe that the CO2 (or pH) fluctuations in our tanks are just natural and are not so dramatic. In nature the CO2 fluctuations during the day are much "worse" (yet it doesn't imply that algae are everywhere). So my personal belief is that plants will be happy with whather CO2 we supply them. Of course, there are some adaptive mechanisms in play in nutrient uptake, but I don't believe that higher or lower (fluctuating) nutrient concentrations may have some really negative impact on plants. T.Barr tries his best to keep perfectly stable CO2 levels, but he doesn't care for keeping perfectly stable levels of other nutrients. Why? The CO2 is also a nutrient. Why should plants need stable CO2 level, but other nutrients may be dosed once a week. When we add KNO3 into the water once a week, then its concentration in water constantly decreases during the week. How is it possible that this fluctuation does not matter to plants? The uptake of all the nutrients is in close relation, so if plants really need stable CO2 levels, then they really need stable supply of other nutrients also! That's the reason I don't believe we really need a stable CO2 levels. We need enough nutrients for our plants to grow well. And I believe that low CO2 levels (10-15 ppm) are enough for our plants to grow very well. So back to BBA (genus Audouinella), I think that most algae need nutrients, light, time and undisturbed environment with reasonable parameters to multiply. In nature BBA is often present in very clear waters with higher flow (they are sometimes used as indicators of clean environment). As they live in quite clean waters (which are usually low in nutrients) I would suppose that may be the reason for them to need higher flow, as with higher flow they get higher supply of nutrients. As I know also, BBA doesn't need strong light to grow (low light is also fine for it). Sometimes we also make a wrong conclusions when speaking of "nutrients". For algae "nutrients" mean not only unorganic but organic as well (together with vitamines and other organic substances). So if you give your algae in your tank all the nutrients needed, and give them enough time to settle down and multiply (without any disturbances like water changes, algae-eaters, plants stealing them light and nutrients etc.), then you will get algae for sure. But if you have enough "disturbing" factors in your tank, the algea may have hard time to take hold and grow well. Some scientists say also that BBA doesn't like too low pH (under 6.5) => it
usually live in the range of 6.5 to 8.5. As I know, T.Barr has 5.9 in his main tank, which may contribute to the fact he doesn't have any problems with this kind of algae.
