Originally Posted by jaybyrd
Something seems to defy all logic bettybaby when you state that an air stone would not work with CO2 in imparting carbon into the water because the bubbles are too big.
The CO2 needs time to allow for the carbon to mix with the water. With the slower amount of CO2 entering the water through the air stone it would need more contact time with the water. The atmospheric oxygen pumped through the air stone at greater quantities allow for the oxygen to be plentiful in the tank at night while the fish and plants still consume this commodity - rather than plants creating it during the day light hours and photosynthesis.
Otherwise I would have some oxygen starved fish in the morning.
Let me try to explain this using a diagram I just created special for you, I hope this will help it make more sense to everyone.
In the diagram I have made examples of an air stone, a limewood block, and a track diffuser. The red indicates the CO2 bubbles, and the sizes they come out vs the sizes they are when they reach the surface. The pink arrows track the course of the bubbles. In an air stone you have large pores which create large bubbles. These bubbles both because they are large and because there is nothing to block their trip to the surface, will break at the surface in a larger form. This does 2 things: it limits the amount of time the bubble is in contact with the water, making for less CO2 dissolved into the water, and it makes for a larger bubble bursting at the surface, so there is more wasted CO2. Using a limewood block has the same situation with nothing slowing the bubbles in reaching the surface, however, the pores in the wood are much smaller than that of a stone, so the bubbles come out smaller, leaving for less wasted CO2 when they burst at the surface. When using a track diffuser, the bubble starts at the bottom and is blocked from going straight to the surface by the lengths of track. The track channels the bubbles to the surface, slowing them down on their trip, allowing for more CO2 to be dissolved in the water due to longer contact time in the water. As the CO2 dissolves along this track to the surface the bubbles decrease in size, thus leaving less waste of CO2 when bursting at the surface.
My previous comments stand, and I hope this helps to explain things better. I never implied that an air stone won't
work, just that it's a terrible waste of CO2 and doesn't allow as much of it to be dissolved into the water, making it much less effective. Using an air stone would make no sense. Any money spent on investing in the track diffuser would be made up for in results and also in less wasted CO2.
I also want to clarify that CO2 doesn't "mix with the water". It dissolves into it. There is a difference.
I'm not sure I followed your reference to atmospheric oxygen. If there was atmospheric oxygen hooked up to the air stone you aren't going to be getting the CO2. The amount of CO2 in atmospheric oxygen is so small, it wouldn't serve any benefits to the plants in the tank.