too many micro brittle stars

they are algea driven if you have lots for them to eat then even if you got rid of most of them in no time you will be back to where you are now. They divid and control the algea that way if the food supply dries up then they simply start dieing off till there is a balance. I would look in to controling algea grouth my kids tank gets tons of them when they all decide to feed the fish for a while. They don't know when the others are feeding the fish. water change will help also.

Bill