Iodine, alkalinity, biomineral content... are as important to Anemones as they are to stony, soft corals and other Cnidarians. Again, "Reef" circumstances are required to keep a BTA.
Both foods derived from photosynthesis and augmented physical feeding with meaty foods are necessary for this species. If your animal is or becomes bleached to a degree, ancillary feeding will become even more important. I suggest meaty foods, no bigger than the anemones mouth 2 – 3 times a week, less if the food items are large. The best are fish based (Silversides of appropriate size are excellent, as are various kinds of shrimps, defrosted/frozen cube-foods, planktonic organisms that can be gently directly baster-placed...), and always of marine origin. Tongs can be used to place food items directly onto the open anemone's tentacles.
Some folks endorse the occasional to regular use/soaking of such foods in a vitamin and HUFA prep. like Selcon. This is not a bad idea.
And a note re post feeding behavior. It is not unusual for a just-fed, digesting BTA to "hunker down", shrink in size, pull it's tentacular disk inward and stay this way sometimes for a few days... Do be on the lookout for egested waste packets... and remove these with a net or siphon.
Disease:
The vast majority (90 some percent) of anemone losses period are iatrogenic... caused by aquarists. In order of likely preponderance these are due to improper placement... Being put in with other too-noxious well-established Cnidarians ("corals", other anemones...), in inappropriate physical settings (too small, new/unstable, too little light), damaged specimens (too bleached, torn, starved...), poor maintenance (not using pre-mixed, adjusted water... powerhead disasters...), damage from other livestock (beaten by large hosting Clowns, eaten by predators, poked by Urchins...) and starvation (wrong foods, too large or small)... and NOT pathogenic disease.
Some symptoms of poor health in anemones include an open, droopy mouth, staying closed all the time, and turning to goo. Bleaching... turning more to completely white is a sign of diminishing health... the loss of endo-symbiotic algae that produce food and oxygen, aiding in the reduction of waste and CO2... Many factors can bring about this condition; heat-stress, poor lighting or photo-shock... The cause here could appear to be "nothing", but I would "step up" the feeding of the one specimen... try three times a week... for a while... And re-direct some/more circulation (likely via a powerhead, submersible pump) toward its general direction.
If your anemone, BTA or otherwise exhibits signs of poor health, what can you do? Remedy the root cause/s of the trouble... Provide better circumstances, remove obnoxious influences/animals, feed it better... Very possibly move it to another system, or return it or give it to someone who knows how, cares enough, has the proper set-up to care for it. Doing "nothing" is not an option... Often these animals outright dissolve... fouling the system, possibly taking most of your other livestock with them...
Avoidance of health issues is of course the better route to go... (rather than the too-late lack of health business emphasize in human health care in the West), with good initial-health acquisition of specimens, long/slow drip acclimation to appropriate quarters, maintenance and placement with suitable tankmate species
