Heliofungia should be kept on the substrate of an aquarium, as in nature they are found on the sand bed. Avoid placing it on or near rocks. If placed near or on rocks, it is capable of falling and injuring itself, or tearing its soft tissue against adjacent rock work.
You want just enough flow to move the tentacles - you don't want them in stagnant water, nor do you want the coral placed in a super turbulent flow area. You also want enough to keep any outstanding amounts of sand (or other particulate matter) from settling on the coral heliofungia.
Regarding the lighting; Heliofungia (and Fungia) are capable of inflating and deflating their tissue in a pattern that allows them to slowly move about to a place of their liking.
Also, beware of any corals that may be in close proximity of the heliofungia's tentacles, as they are loaded with nematocysts. Feeding once or twice a week is good. Make sure the bubble coral and the fungia don't get in a scrap, as it looks like they're a little bit close. I've seen some pretty long sweepers on bubble coral.
my .02
