Using a swiming pool pump and filter to remove the solids, bad idea, cause they get trapped in the sand filter. Thus need backwashed on a regular basis to remove the solids from the water flow. I believe this is causing wild swings in the biological oxygen demand (BOD) and thus the reason the system's ammonia (nitrogen cycle) swings are so crazy. The fish are not eating on pace for their age. I added a new drain to allow the water higher surface area as it "drips" instead of pouring into the tank. I drilled small holes into an extension on the return drain pipe, the expectation is that this will increase the surface area, oxygen conversion rate and help the nitrogen cycle.