We have a pink and green bubble. They are fairly hardy, not like a mushroom, but seem to tolerate different salinity, temps and PH levels etc. I have found both flourish if temp is maintained around 80.5, salinity .021 and PH, Nitrites, Nitrates, Phosphates and Calcium are at optimum levels. Depends on your size tank. e.g. my 90 gal reef is at 450ppm optimum calcium.
I digress....I have mine in medium flow under power compact lighting. You will have to move them around in different areas for about two days at a time to see if they like the flow in that spot. They completely close up showing their skeleton at night with the lights off. However it's not actually exposed. The thin membrane of the bubbles lining at the base hugs the framework so tightly it looks exposed.
I will spot feed them every other day with mysis shrimp. I will use an eye dropper and very gently squirt a few shrimp onto their feelers by the inflated bubble pods. Hard to miss as they look like little stubby tentacles. They will close up around the caught shrimp.
In my case a good indication of water health I watch my bubbles. If things aren't quiet right they wont blow up too much. If things are perfect they are in full bloom.
Sorry to make this long. Hope it helps a bit.