I did this in my “planted“ reef. It worked fine for the first five years, but by year six the sand layer on top had pretty much found its own locations with the water flow, fish, cuc, etc, and the mud worked itself upwards, so it got exposed, which caused it to kick up everywhere. That ended up causing issues with my pumps, etc. Now I have a separate refugium with a dedicated compartment specifically for the mud bed and my remote DSB so that it doesn’t get kicked up into the flux.
As far as nutrient sink goes: to be honest, in 13 years of running DSB’s and mixed mud-sand beds, the only time I had excess nutrient issues was my own fault. I was culturing my own phytoplankton and copepods, and back then we didn’t really have good options for fertilizer for phyto production. I used some plant fertilizer when I ran out of the lab stuff I was getting from the university, and at the time I was feeding phyto rather heavily for my crinoids. I caused a nitrate spike that was too high for my sand bed to handle, had a bloom of hair algae and aiptaisia, then got both back under control with an additional nitrate reducing sulfur reactor and nudibranchs. It was a valuable lesson, because it showed two things: 1) A DSB is great for long term steady habits (like heavy feeding over years and years) but not for nutrient spikes caused by stupid, and 2) don’t substitute inferior products for critical systems.
I don’t think DSB’s are really well understood by the pundits today, but I also think you have to really look at what you’re wanting to accomplish to decide if you want one or not. If you’re a planted tank person moving to saltwater, I really cannot recommend
this book by Julian Sprung enough. Soo many of the youtuber types are doing videos on “discoveries” that are already written about in much better detail in that book, and the tips on plumbing alone will save you a whole lot of heartache over time. It’s dated on some things, but for the most part, the science is proven and it’s a really good nuts and bolts manual.
With that all said, I did move over to remote DSB and barebottom display. Even us old dogs can learn new tricks. Not because DSB doesn’t work, but because I’ve moved on from lagoon type mixed reefs to high energy, high flow SPS keeping in an acrylic tank, and I don’t want sand blasting scratches across my display with time. There Is still room in this hobby for MANY different approaches, and even ones that are popularly considered bad ideas can still have merit if done right. You just have to decide what your end purpose is, and don’t be afraid to embrace the lessons of failure!
Happy reefing!
