My experience is limited to entacmaea quadricolor (bubble tip anemones) of which I have 15 - 3 of which over 1 foot across, all clones from 2 tiny BTAS a few years ago. It's not usual for anemone to have "private moments" where they shrink for a few hours. If they shrink for several days they're either a) preparing to clone (split) or b) sick or starving. Some literature suggests it may be a) and b) (i.e., they often split when stressed). The following text grabbed from some online FAQ (forget which) claims that H. malu are among the more difficult anemone to keep in captivity and often perish within 6 months. It sounds like they need a lot of light.
Key things I would check:
1) Check water params again (particularly salinity and pH - anemones are very sensitive to rapid change in either)
2) Confirm you have sufficiently bright lighting for your tank
(MH lamps).
In my experience, good light is more critical to anemone health than
solid foods. They also need good circulation but not direct shearing
discharge from a power head.
If all this stuff checks out, I wouldn't change anything - just keep a close eye on the anemone. You usually don't need to worry about
them poisoning your tank unless they release they're grip on the substrate and float away or there are obvious signs of decay or release of stuff into the water. Definitely don't try moving it unless
you're convinced its dead and about to poison your tank.
Finally, I've had BTAs survive trips through the overflow and sump
where they look shriveled and awful for many days, bleached, etc
but bounced back fine when returned to a well lit spot with good circulation and a comfortable foot-hold. Hopefully yours will rebound as well and/or you may be "expecting" a new clone soon! Cheers.
"Difficult to keep anemones
Heteractis crispa or H. malu, Sebae anemone, Singapore anemone, pink-tipped (but not condylactis) anemone
Tentacles range from long and thin to short and fat depending on the condition of the anemone (short and fat usually means it is starting to waste away). Tentacles usually have magenta colored tips although yellowish-green tips are not uncommon. Colors can be dyed yellow, dyed pink, natural pink/purple, natural yellow, tan, but by far the most common is pure white. The oral disk may also have a green sheen under actinic light.
Good Points-They are very common in stores and are usually the least expensive of the host anemones. They are accepted by virtually all clownfish whether they occur together in nature or not. Some not so white specimens can regenerate their symbiotic algae thus becoming a brown color. If you can obtain a tan specimen with long thin tentacles they should do well under conditions similar to that required for bulb anemones.
Bad Points- No one I have spoken with, not even the public aquariums, can keep the white or yellow ones alive for more than 6-8 months. Out of the over 20 responses I received regarding sebaes only 2 anemones had stayed alive for over one year. Both of the anemones were tan in color either when purchased or had turned tan shortly there after. One thought is that sebae anemones may expel their symbiotic algae shortly after capture and when it is completely gone it is not easily replaced. Frank Greco of the New York Aquarium says that he has been successful in getting otherwise healthy sebaes to "color up" by feeding once a week with fresh fish, clam, shrimp or gelatin. They also get live brine shrimp, adult and baby, and a yeast based diet of his own design. In addition to the frequent feedings the anemones are exposed to very bright light, three 400 watt metal halide bulbs over the six foot by six foot, four foot tall anemone tank. If the anemone is not able to replace its zooxanthellae it is doomed to a very slow starvation once in the tank. There are cream colored sebae anemones found in shallow water in the wild, but they are not the transparent white color found in the dealers tanks. These don't seem to be a good beginner's anemone despite articles I have read that say they are. "
