I'm looking at ordering a custom tank to have a 150 gallon shallow reef tied into my current system which is a 350 gallon display with 180 sump. I would add a 125 gallon sump under the shallow reef to get extra water volume. The two sumps would be tied together by drilling holes in each and using probably a 1.5 inch bulkhead and pipe to enable good flow between the two. I would probably use a 3/4" return line from the 180 sump to go back up to the 150 shallow reef. I built a diagram to scale to show my planned plumbing. The only thing that isn't right on the image is the shallow reef will be at a 90 degree angle to my current tank, not in a straight line, and I would put a ball valve between the 180 sump and 150 shallow reef to control the flow.
I'd appreciate it if you guys would give me a sanity check on this. Return lines are blue, drain lines are red:
I think the return pump would send water from my 180 sump into the 150 shallow reef which would then drain down into the 125 sump. The water would gravity feed from the 125 sump over into the 180 sump. If the pumps all stop, the 350 tank and 150 shallow reef would drain down to the top of the drain in each tank. The water level in both sumps would rise equally to stop at whatever level I had previously set. (I would determine the total volume by turning off all pumps and filling my sumps to the max level I would ever want, then turn on all the return pumps and mark the resulting water level as my max fill line).
Because I want my shallow reef low enough to look down into, it is set much lower than my current display tank. Dimensions would be 88x27x15 high. There would be little room between the top of the 120 sump and the bottom of the stand, so I would probably only use it as a cryptic zone with rock, bio media ceramic blocks or balls and no lights.
Please post your thoughts about this design and point out any areas you see that could result in a failure of any type.