Now, is "filterless" (Skimmer, LR, and ph only setups) feasible for reef tanks with a significant number of fish (or a significant bioload)?
I know of someone who has LR, bear bottom, powerheads, and a Deltec skimmer. And that's it. But he has more corals than fish. He probably only has a mandarin, a yellow tang, and clowns in his 100G tank. No sumps etc.
There are lots of examples at reefcentral as well. Chris (the guy who had the setup above) said that he has all those powerheads moving the water in order for detrius not to settle at the bottom. Then the Deltec skimmer skims the c r a p out of em.
I really believe in making things as simple and as efficient as possible.
When hobbyists go for sumps and fuges, auto top offs, complex electricals, Kalkwasser setups, complex plumbing, closed loops, etc, etc, that they're just really into the hobby of creation. And there's nothing wrong with that. I do see some amazing setups due to efficient use of all the above. But I believe that their fondness in the hobby is more towards the DIY fun than the specimen fun. I don't want to generalize, though, because I've met the ones that use the above and are very passionate aquarium activists as well.
It's just that when I see someone who placed so many hours, efforts, disasters, leaks, and all that, and looks somewhat similar to a setup I ended up with, I start to question the mileage covered for a somehow similar destination.
With that said, rock on, for people that enjoy DIY. They are all amazing masterpieces that are clearly fun to see.