[Sk8r]

You will get different readings on ph at various times of day. The rest will be steadier, and that natural fluctuation is harmless unless you ride near the border and it dips or rises extremely.
If you have ghosty problems, and have not done a several-times-a-day ph test, you might look at where you fall.

Re respiration: that's an interesting question, since these corals 'eat' light by this process: their zooxanthellae [big word for little plants] algae [which they have inside their flesh] suck up sunlight and nutrients and generate food the mushroom uses to spread out or reproduce. It could be cyclical. I don't think I've ever heard. But if you've ever seen a shroom ooze brown stuff, that's a OMG-TOO-MUCH light reaction, usually, as it rids itself of its internal algae to try to balance out. It then gets a suntan [browns] to try to minimize burning. So yes, a lot goes on with the aspect of corals that is 'plant'. I have never been convinced one way or another, but I have always found shrooms and the like don't mind a squirt of phytofeast or DT's phytoplankton. Certainly it helps support microorganisms like pods, which corals do eat. [Any coral will eat most anything it can suck in, and shroom mouths, while operating a bit like a strainer, are quite large, so I'm sure they eat pods when they can get them.]

I used to raise quite a lot of buttons and shrooms, and I'd still have them, but they don't always get along with my stonies, and I REALLY had a bloom of them in my last tank...they completely covered one rock and were headed for the rest,one even growing on the downflow wall. [Discosomas, you can figure!]

But they were thriving on the 1. good water 2. phytoplankton doses, whether primarily or secondarily [via eating things that grew because of it] 3. decent flow. and me having a decent skimmer, they got oxygenated, which probably helped a lot, too.

For anybody that wants to play with a theory of mine, I think one thing they REALLY liked was the Sea Swirl...it takes a straight-line flow and acts like your lawn sprinkler: it sits on the edge of your tank, you route your hose through it, and its nozzle swings lazily back and forth. This results in a lot of things getting stirred up, both detritus [but not in a bad way, and shrooms like a little] and just the edges of the shrooms ruffling up a bit in a continually random way. Anybody else have one of those? You sometimes see them for sale second-hand in the Used Equipment forum. Just guesswork.

I think with shrooms as with any coral changes should be slow, the water as consistently sealike as possible, though gentle flow is probably a good thing.

Note: have you ever noticed that the structure of a mushroom and that of a zoa, of an anemone, of a large polyp stony, and even of an acropora stony---are all identical? You have a mouth, a disk, and tentacles however stubby or extravagantly long that sweep food to the mouth. The mouth widens and it sucks hard if there's food in the water, the tentacles move it in; it excretes by the same aperture. The only difference is that shrooms and nems can 'walk'; buttons can only grow to expand, but all share a common tissue, so all get the food from one lucky polyp; the hard stonies have one new ability---excreting calcium into a skeleton, via pores in their base---which doesn't let them move, though they can build their tower taller and taller and branch it sideways: they again share a common tissue, and what one polyp gets is shared by all.

A lot of the earth's history starts with shrooms.

HTH.