Framerguy, the benefits of a RUGF is that IMO it is the longest lasting, least maintenance systems available. As you know my reef has been running since 1972 with this system and I only cleaned the RUGF twice.
The advantages of it are that I can use gravel instead of sand which can accomidate many more pods between the grains as opposed to sand where larger fauna like pods are restricted to the surface. Also due to the flow of oxigenated water, the entire bed is full of bacteria with little chance of hydrogen sulfide occuring. The interfaces of the gravel, in time will build up detritus limiting oxygen in those small places and allowing anerobic bacteria to convert nitrate.
There is some maintenance but the system can last indefinately (or at least 40 years) with no replacement of parts or gravel. Due to the nature of the system with the water flowing through the gravel, you will get some detritus which as I said is not a bad thing. But if left alone for 6 months or a year you may get too much of it. Every three or four months I stir up the gravel where I can easily reach with the outflow of a diatom or canister filter and suck out the detritus. After about ten years I do a more thorough cleaning by moving some of the smaller rocks and stirring better. At 25 years I lifted the UG plates, mainly to see what was growing under there which was mainly tiny bright red tube worms. There was very little gravel clumping, no hydrogen sulfide and generally healthy looking gravel.
To run this system you need to push water through the gravel very slow. I run 50 GPH through each "lift" tube. You also need a filter of some kind on the intake before the water goed under the gravel. The better this filter is, the longer the system will last between maintenance. I have my three tubes plumbed together and I use one pump for all of them. I also use a sponge on the intake but I used to have filter with a settlement chamber connected that was a much better method. A sponge lets too much detritus through.
The slower you run the pump, the better.
If this is going to be in a refugium I would stir it more often as you don't have old corals growing all over the place.
UG filters are no longer used (except by me) because people try to use them like we did in fresh water by running as much water as we could through them from the surface down with no filtration. That system will not work longer than a few months to a year in salt water. I have tried it and it was a nightmare. When this hobby started, that was the only way to go as there were no filters or sand sold specifically for salt water. We all used UG filters and many people were forced to get out of the hobby until a better system became available. I personally do not like DSBs. It is only my opinion and my very first system in about 1971 was DSB. They have a lifespan and can't be maintained without tearing them apart. I know all about the "critters" people throw in there for this but those animals can only live in the oxygen rich surface areas of that type of substrait. I collect these "critters" all the time under rocks on muddy beaches and you only find them under rocks where there is circulation and oxygen. These places are full of crabs, worms, amphipods, mussels etc. to the extent that there are no places on that rock that is clear of animals. But when I lift a rock next to it where the rock is stuck too deeply in the mud, there is absolutely no life, just anerobic bacteria producing hydrogen sulfide which you can immediately smell and see by the blackish purple mud. I know DSBs in aquariums are not the same as a muddy beach so there is no need to jump all over me. It is just my observation from over fifty years of looking under rocks
Yes very wierd I know. Most people walk the beach either fishing crabbing or shell collecting, I am looking under rocks.
Anyway have a great day.
Paul