[smokinreefer]

i, like troy, have found xenia to be a most mind boggling creature.
i have kept xenia for several years and i still do not know what makes it tick.

FWIW, i have some xenia elongata, the most common of the xenias, and while most people find this xenia to be extremely easy to keep and display rapid growth and spreading, that has never been my case. although it remains healthy, it barely grows/spreads.

i do have great success with another variety of xenia.

i would not chase numbers of alk/pH in hopes of enticing the xenia to pulse. if your tank is healthy and stable, i would leave it that way. my water parameters are fairly stable, that is, any changes dont occur overnight. but i have kept xenia in low and high alk, probably pH as well.

though my xenia has never stopped pulsing altogether, it has slowed down at times, and at times it pulses very rapidly.

i don't think water flow or light affects its pulsing either.
i have some xenia near the top of my tank (400W MH) and right infront of a powerhead, and it still pulses. i also have some xenia on the sand bed, and it pulses.

i know that doesnt help you much, but i personally would just let the xenia be, as long aas it is still healthy.

the only thing that pops into my mind is this, perhaps the xenia pulses in order to feed itself. if this is the case, you think the xenia would regulate its pulsing on how much food source is readily available in the water column. more=less pulsing, less=more pulsing in order to meet its feeding demands??? just a theory.