As I understand, generally bioballs will only reduce things to nitrate.
The end result of using a DSB, or LR for nutrient processing ideally results going one step further, leaving nitrogen gas - not nitrate.
Thus it's only part of the process. IMO, you could probably run 3 different devices for moving things from amm. -> nitrite -> nitrate ... but when one works fine, why do it with three?
Thus if you already have other methods, that allow the possibility [even if imperfect] to further reduce ... why extra redundancy in bioballs for a `reef' tank?
For a fish only or other use, the w/d is mighty useful [esp if high bioload].
Or if it didn't collect lots of debris, become a rarely maintained device all too easily [ever cleaned one? I'm sure glad I'll never do that again]
My opinion, ignore if you don't agree
