Thanks for the feedback Rob. The overall volume without sand, liverock comes to around 200 gallons. Correction on my part - the pumps will be 2 x apex cor-20 and not cor-15 that together have the capacity to churn 4000 goh which is 20 times the water capacity. Over and above I have the apex wav kit ( 2 wavemakers) factored in and will be added as time passes. The apex wav at full capacity is another 4000 gph. The close looped system will be as follows: - 2 or 3 pipes drilled mid lower section at the back - a web of pipes connecting via a T spread across the entire bottom with Flare nozzles for the output - pipes buried in the scape rocks with low profile bulkhead overflow strainer as the output. This set of pipes will be tuned not to spray and full capacity with option to tune in as and when required - all closed loop return pipes will have check valves installed - 1 each at the pipes and an additional one on the main line as a backup Ozone- love to have it and on my priority list however yet to figure out the spot for the ozone machine away to avoid issues with family around Regards, Allan Sent from my iPhone using Tapatalk