Yes it is...and when the algae is gone or they are staying ahead of its growth, its possible for some to die of starvation. As long as I can see algae growing here and there I do not worry about their getting sufficient food to eat, however most times I also add a piece or Nori for them to eat as well for those times there is not enough algae growth to support them. You can get it in dried sheet form, tear off a small strip, roll it up and place it on a small piece of rock and secure with a rubber band and drop it into the tank in a location I can retreive that small piece of LR for use again when I feed algae another time or use one of those stick on clip feeders to attach the algae to.........