Nobody answered yet, then allow me add my 2 cents worth. But: I'm significantly less time in the hobby, if you see any faults - make corrections.
Most have large rectangular tanks with more than enough space for pumps (or powerheadls on wavemaker) placement and, what is important, enough space for aiptasia eating fish, copperband butterfly or marine betta (comet). If peppermint shrimp or aeolid nudibranchs worked well for you, then no problem.
Is 8" width or height? This is not NPS, but nano-tanks specific:
- possibility to put hand in the tank to pick up or place anything, that can't be picked/placed by tongs,
- enough space for hand plus syringe for treating aiptasia under the rocks,
- place sources of flow, even small powerful powerheads have minimal physical size. Several of them (or tubing of closed loop) could be necessary to sweep out powder-like food leftovers from under the rock AND up, for removing by filtration. And keeping food suspended in water column for a long time.
- Depending on type and amount of corals, that you plan to keep, even vast amount of pods, bristle worms and hermits with snails could be not enough (I already tried refugium type of tank). For me access for cleaning was important.
- most gorgonians are 7"+ high, some inflated dendronephtyas - too. If the flow in upper regions will be directed on them and be strong - this part of polyps will not open for a feeding. Some improvisation with flow, reflected from glass or rocks, before it reaches corals, could be necessary.
- clean up crew should be proportionally sized, like very small snails ($4 each here) and small blue legged hermits. Even astreas, not mentioning turbos and medium hermits, are wrecking havoc in the tank, and picking up after them each morning is not fun at all.
Apart from physical size limitations for hand, hardware and aiptasia eaters, this kind of tank could be as good as any other.
My personal preferences are cubes with rounded corners, hexagons, round and half-round tanks, allowing reflected flow around, but I tried only first two. Now have shallow 6" tall tanks for smaller corals and 12" high for taller gorgonians.
With shallow tanks the only problems is with setting flow between, around, but not above corals (not enough place for dissipating cone of flow, that become wide at short distance).
Sump with good filtration/skimmer on hang-on equipment may be necessary.
Some are suspending dendronephthyas, chili coral and sun corals, but all mine disapproved this.
HTH
