It should be once a week all the time, daily if you are having problems.
Have you tested nitrate and phosphate? It sounds like you are overfeeding and doing far from enough water changes, too many nutrients in AND not enough out, way out of balance. This is exactly what causes algae problems.
I wouldn't broadcast feed. What kind of anemones? I would feed something large and meaty so they eat it whole with no waste, like silversides or big chunks of shrimp, scalllops, etc.
You don't need to worry about zoanthids or polyps. The best light for growth (zooxanthellae) is redder than you want to use, same as plants at around 6500K. They will be brown and ugly though. Most people use white light that is 10,000-14,000K and actinics. The actinics 'tan' corals, except than instead of tanning brown like humans they tan fluorescent colors. So without the actinics providing the UV to make them color up, they will be an ugly brown.