Suppose there are 500 units of energy available for the producer level of energy pyramid approximately how many units are in it are available in the first level consumer

Always 10% of the energy is passed on to the next trophic level and 90% is lost... mostly heat: so if the producer has 500 units of energy then the primary consumer has 10% fromm 500 = so 50 units of energy is passed on to the next trophic level.

Distillation.  distillation is the correct answer.

Although i don't know what is the simulated system, starfish are predators that eat mostly  microalgae,  snails, sponges, bivalves, mussels and other small marine animals. removing starfish from any system would definitely increase this animals that they prey.