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thanks for bringing that up, it's an important point to state that a lot of reefkeeping edicts aren't really fact...that air exposure is harmful always is just one. Another is that nettline/allelopathy will result anytime you blend corallimorphs and stony corals. Although they are fine guidelines, they shouldn't be stated as exclusive fact because the adaptability of corals changes things over time.
These corals seem to become sensitized to each other's chemical signal over time, that's how they all share a gallon for about 4 years now (with rearrangements as needed of course to prevent direct physical contact)
and when draining it I just do it before lights on so the lps aren't expanded and full of water. sometimes it'll stay a full minute drained if I don't have the water perfectly ready, and once I even left it drained for about 5 minutes when I got a phonecall amazing enough timing lol. the corals react by sliming up for a sec to hold in vital moisture, then it's sloughed off when the current is turned back on and the shrimps eat it all up.
i think there are certain sponges that shouldnt be air exposed, but the ones that showed up in my tank are adapted to this type of maintenance.
Lastly, for any of you with small algae patch problems, you ought to consider draining your tank down for a spell so you can shoot the algae patches with a blue jet cig lighter and burn them off. I've done this to aiptasias too, works great. funny idea eh? ever heard of anyone using a pinpoint jet lighter on reef maintenance? try it! the rock is too wet around the perimeter to conduct much heat, and if you are in a tight space you fold tin foil to serve as a shield for example if you are working at the base of an SPS coral or something