Hey Marc, do you prefer to siphon the water out or would it be easier to add a bulkhead low in the return and skimmer section to just drain it ou during water changes? I have been thinking this process over and I never enjoy the process of having to start the siphon for each section and what not.
The siphon system is pretty simple with my circumstances. I've made it a point not to put any permanent plumbing across the walk area, and I've not drilled any holes or cut out any of the gridwork on the french drain. I'm trying to avoid any items falling into the drain that wouldn't be recoverable, nor do I want to accidentally have the step ladder's foot snagged or cause me to fall. I have an acrylic box I made that locks into the grid and the drain-end of the tubing fits into this to direct the water into the floor drain. Because it was made with clear acrylic, I've kicked it about half a dozen times and the last time broke it. I'm going to remake it but with black acrylic so I readily see the darn thing. I'm able to siphon out virtually all the water in the two zones, but drilling holes and inserting bulkheads wouldn't allow it, leaving about 3" of water beneath them. Not drilling down low eliminates yet another risk / point of failure. The new hole that was drilled works great for the water change, but it also is something I may use if I tie in a secondary tank to house the anemones and angel fish.