I too have read this and is hotly debated, well the skimmer that is. I think DSB's in the long run are beneficial to a tank. Think of how deep the sand bed is in a reef and that should tell you everything. They harbor a ton of the life that a skimmer pulls out that essentially is food in the for the chain. Have you seen a skimmer in the ocean?
I had a DSB in my system and it did great. Many have the same results as I did, where the DSB starts taking over as the main denitrification processor. One of the issues with a DSB over the course of a couple to few years is that it will stop denitrifying. There are more organic and inorganic compounds on the sand that it cannot break them down fast enough. The other issue is that the sand cannot be disturbed--vacuumed having sand sifters of any kind.
The issue that I have with skimmers is the amount of food that it takes out of the system. That gunk that we all see pulled out by the skimmer is food for many corals and photosynthetic corals/inverts. Many won't argue with this. But they will argue that this gunk the skimmer is pulling out is essentially the root cause for algal and diatom blooms. Fair enough. I have never personally been in an oceans reef, but there is a ton of algae and cyano on the reef floor from the pictures that I have seen. So, we "are trained to freak out" when we see algae or cyano on our systems. So what do we do? We buy skimmers, reactors, chemicals, etc to combat it. Even though it is a natural part of the ecosystem in reefs--it too is a food source and many algae's absorb nutrients.
The other major problem is that in order to have a good skimmer, you are also paying top dollar for one. Even used skimmers fetch a pretty penny. Like my skimmer, eventually, it will stop pulling gunk out. For the first year+ my skimmer pulled a ton of cr@p out. No joke! But eventually, the system got so dialed in that the skimmer stopped pulling out gunk. So I was always adjusting it. I have also read many threads where other hobbiest skimmers stopped pulling out organics regardless of the amount of tweaking they did to it. So the skimmer becomes useless and very expensive piece of equipment that eventually will stop pulling out organics (skimmers don't pull out inorganic compounds).
So, my advice is definitely use a DSB. I think they are worth the investment. Skimmers on the other hand I don't understand why they are needed when many systems have been around for decades without one and are thriving. Maybe its a marketing ploy, who knows. But many swear by it however, the only argument they can make is they pull out organics so the system can stay "clean". If you do get a skimmer, spare no expense in getting a good one. At least if it does stop pulling out cr@p, at least you can resell it and get some of your money back.
I personally am going to go the DSB again on my next system. The only difference is that I am going skimmerless. I am going as natural as possible without using to many amps (watts); I am going the ATS route with a bunch of macroalgeas, bunch of CUC, and plants to pull our additional in/organics in the sump. An ATS also acts as natural chiller as well so they can keep the water relatively cool. And I am going to need it in Hades (Phoenix). I hope this helps Jesus!
