I have read this whole thread and some of the papers linked. There has been a lot of back & forth with a lot of strong minds (and wills) but not a lot of proof from the couple of major proponents of the processes major claims with regard to nano bubbles. Let me start out by saying I'm just getting started in the hobby and my system is not up and running yet. So I'm not here to confirm or deny that there are positive results from "Bubbling" at night. Nor am I here to state "Nano-bubbles" can or can't be created with the use of hobby grade air and water pumps. I would think that there is a chance that a very small percentage, probably <5% more likely <1%, that could, if even created, theoretically accumulate over consecutive nights bubbling.
While I have not got any experience with reefing I do with fishing, angling. The type of fishing I mostly do requires the keeping of bait fish, mostly Blueback Herring, and I have used most of the products available to help keep the bait healthy. Granted this is not long term, generally through a day maybe two at most. The
Keepalive bubbler does a very good job of creating a fine mist of bubbles but in the hotter months it transfers a lot of ambient heat to the water column of the bait tank which I'm trying to keep at 65 to 68 degrees. I am currently using their
O2 system to reduce this heat and to reduce the use of a recirculating pump that is on all the time.
I bring this up because after turning either of these systems off there is a coating of bubbles on the sides of the tank, even on the sump side that has no direct exposure to the bubbles. This is due to the gas precipitating out of the water. Just like when pouring a glass of water from the tap. The aerator and screens in the faucet adds air to the water. If the water is left to sit and as it warms the gas will precipitate out of the water on the sides of the glass and anything else in the glass.
I understand that micro bubbles will attach to suspended particles in the water column and to most anything they come in contact with due to surface tension. I have not seen anyone report any bubbles that may have formed from precipitating out on the glass or any other objects in the tank. If there is any precipitation in the tank it will help lift heavier detritus off rocks and the sand bed.
I also have not heard anyone state whether the initial slimming over of corals is good or bad. My 1st thought is that this is a defense mechanism to a irritant from an external stimuli. That it ceases after a day or two would mean that it has become conditioned to the stimuli or that it's not sensed as a threat any longer. With PE I would think that after several consecutive nights of running that the nutrient load has dropped in the tank and the polyps are extending further in an attempt to capture more particles.
I wouldn't view this as turning the whole tank into a skimmer. More of a "Micro-bubble" pre-skimmer which will aide in the removal of detritus and unwanted organisms to the actual skimmer where they can be efficiently removed from the system. With the added benefit of increased oxygenation of the water, a more stable ph during the non-photosynthetic periods and the
potential to help with nuance algae. (It would be nice to see some long term results, six months plus. Especially with nitrates without carbon dosing.) None of this sounds bad to me and all of it without the use of the word "Nano".