Triple drain apparatus for an aquaculture system tank for reducing water input requirements and minimizing breakdown of solids whereby the solids are larger and more concentrated when removed from a solids settling device. Water flow is split by the apparatus into a side box fluid stream which flows into a side box coupled to the tank, and both a clean fluid stream and a high solids fluid stream which flow into a center drain. The center drain comprises a central stand pipe coupled to a clean water outlet, a sump coupled to a high solids fluid outlet and a collection plate separating the tank and the sump. The center drain may include a mortality trap coupled to a mortality outlet and the sump, whereby the collection plate separates the mortality trap from the sump, to provide means for easily removing dead fishes and large debris from the tank.