@ jeeba: Ultimately, h2o can only hold so many extra oxygen atoms in solution (bar supersaturation). So the stone has no actual effect on total dissolution, that's what the experiment proved. The reason there is now confusion is because legally and woodsman are saying that the stone DOES make a difference(due to bubbles being smaller). Providing max DO in a container, as proven, can be done with a relatively small pump and just about any stone. To get more oxygen to the roots you then need a bigger pump not a different stone, unless the stone has a max airflow rating lower than the pump's. It's no longer an attempt at dissolving more oxygen, but creating a constant supply of air pockets (bubbles) around the roots themselves. Think of an aeroponic system. The roots get oxygen primarily from their surrounding air, not DO. Once max DO is reached, that's it. Providing more air flow only changes how much volume of undissolved air is present for the plants. More undissolved air is a good thing, it's just not caused by stone "upgrades", and I need to make sure that's clear.
Think of it this way: If a garbage bag can hold 50lb of baseballs before it rips, does it matter if the baseballs are whole or cut into halves or quarters? No, they're still going to weigh the same amount, and ultimately, the bag will not get stronger just because the baseballs are now smaller.
Likewise, if a factory can produce 20 baseballs per minute (pump's airflow), it doesn't matter if they ship them in 10 trucks of 1000 or 1 truck of 10000 (surface area of bubbles). They're still only going to produce 20 baseballs per minute. It's faster to unload 10 trucks of 1000 because you can have more access to the baseballs and therefore more work being done at once, but in our case this makes no difference as the supply of bubbles (baseballs) is constant regardless and we only have so much space to keep the baseballs (DO being maxed out). So even though they can work faster, they don't, there's no change because speed of dissolution, or unloading the trucks, was never a factor..
The diffuser should have smaller bubbles unless they're coagulating. I'm honestly unsure about the conditions required for that to happen, though I read through something yesterday that talked about it. I'll try and find it again. Ultimately, my point remains same: Your 80lpm pump, whether hooked up to 1 epdm stone or 1 blue stone, will provide roughly the same amount of airflow, provided that the stones' max airflow is at least 80lpm and their resistance to flow is similar. Legally said his diffusers were more restrictive, so the diffusers will actually flower less air, probably not any substantial amount though. I can't find specs on the cheaper stones otherwise I'd be able to have a definitive downside of diffusers. But you can see a very clear difference in total water turbulence when running the blue stones over the diffusers, due to a less restrictive flow of air. Regardless, I have 10 buckets to aerate, so for me to max out the airflow(not DO) of 10 airstones will take a lot more air pump capacity than I care to have no matter what stone they are. And no matter what stone they are, DO will be the same. Resistance to flow is more important than bubble size, as this will affect how much air can be constantly present for the plants vs bubble size which affects only the rate of solution(irrelevant here).
If, however, I upgrade and have 5x250lpm pumps and my stones can only flow half of that, yes a stone add-on or upgrade may be warranted. But not even to a diffuser, as legally said himself that they were more restrictive. Larger or more stones would do the same thing. And again, that won't change DO(which was already maxed out), but will provide more total airflow to the plants. Because more oxygen (not dissolved) will be present, and more oxygen is generally better, the plants will then benefit.
Moral? Pump upgrades are more important than stone upgrades, unless you already maxed out your stone's airflow. To check this on a 2+ outlet pump, close one outlet and see if the airflow on the other changes. If it does, your pump is not able to push as much as as the stones are able to flow. If it doesn't, you may want to look into stones that allow for more airflow. That way, your pump and stone capacity is about equal.
