Oh my gosh there so much opae 'ula. There are about a thousands of shrimp inside that tank. Looks like they are eating spirulina at the top of the water. We get this shrimp by big island by ordering it here. The opae'ula needs some light to live not to little and not to much or they will die. They can also eat algae. Some shrimp of the bottom left of the picture is resting on the rock and that is why you need accerice