Here's my somewhat unusual setup. I wanted to have one system (more water volume) but didn't want my soft corals to overrun the LPS/SPS, so I set them up as two different tanks.
All three tanks are connected via DIY acrylic overflows (u-tubes) and the 15" cube on the end is drilled and has a bulkhead. Water flows from the 25---- to the 20---- to the 15" cube--- to the sump--- and back to the 25. Flow rate is low, maybe 150gph.
The LPS/SPS tank is a 25-tall. The softy/LPS "Royal Rumble" tank is a 20-long. I built a drawer box (junk drawer, lol) to build the 20-long up to the height of the 25. I have enough room on this stand to remove the 20-long and drawer box to put a 75g beside the 25. May eventually do that... maybe.
The 15" cube on the end is one I custom built from a "recycled" broken 75g tank. Will be a frag grow out tank as soon as I can get a light over it.
You'll notice they are all about the same height, so they fit under the canopy. I designed and built the entire stand/canopy at the shop here at the Seminary in Wake Forest, NC.
Here is the setup with the sump/fuge. Sump on the left is an old 40-tall. Fuge on the right is a 29g. Skimmer in the sump is a Coralife 220. It's run by a terribly oversized 1000gph pump but is working great.
FTS of the 25:
This is a mixed tank, and I just put a 250W DE halide over it. I had a 4X24 Nova Extreme but recently sold it when I got the halide. I also have 8 high-power Cree XRE royal blues for actinics and it makes a HUUUUUUGGGE difference.
FTS of the 20: I call this the "ROYAL RUMBLE" tank, since I allow things to grow however and wherever it wants. Lots of xenia, kenya, anthelia. The red goniopora was in the 25, but it just was too powerful of a coral killer so I put it in here, seems to really like it's spot. This has a 4X24 T5.