They got away from UG filters because we used to use them in salt like we used them in fresh water and they will crash in about a year if you do that. Trust me, I know that.
But if you run them very slow and in reverse they let your tank last forever which is why in about 18 months my reef will be fifty years old. Try to find an old tank with a DSB.
The reverse UG filter pushes oxygen through the gravel all the way to the bottom so life can live there and the life there is what feeds the corals and allows pods to flourish. I need that microscope life because I keep a lot of pipefish, mandarins, bleenies and other small fish that depend on that stuff.
There are very, very few people that run a reverse UG filter, you can count them on one hand, but those tanks are the oldest and have the least problems. You don't see UG filters for sale because they are cheap, not much money to be made and they got a bad rap because they crashed tanks when they were run the normal way as the instructions read.
I built a small plastic manifold from a HOB filter and the 3 UG filter tubes go into that. A powerhead pumps water into there and it evenly goes down each tube at about 1500 GPH for each tube which is very slow. If you pump too much water down there, the gravel will clog. That is why they got a bad rap.
I use the diatom filter a couple of times a year to stir up the gravel to make sure it doesn't clog. That is also one of the plusses of a UG filter. You can maintain it as most systems you can't and nothing lasts forever without maintenance.
My fish all die of old age, all the paired fish always spawn (even the 28 year olds) and nothing ever gets sick for their entire life. I never have to quarantine anything. I am not sure how much the UG filter and diatom have to do with that, but the system seems to work as I have never posted on a disease forum.
There is no "New Gear" that I use. I am very old school. I did run an Ozonizer for decades but it died last year. I will get a new one when I get a chance because I like what it does for the water and if you put the Ozonizer hose up your nose, you get a big rush. Of course your nose rots off but you just have to get over that.
This video was 2 years ago before I moved the tank here to my new house. That is a feeder I designed to distribute new born shrimp mostly to the mandarins and pipefish which are all spawning.