With biological filtration with any media there are pros and cons to all.
Liverock can carry creatures into the water, bioballs offer less space for bacteria, and the different stone or glass media can easily get clogged with slime that inhibit the colonization of bacteria within.
With any of the artificial media the greater efficiency of the product the more cleaning of said media your going to be doing as well.
That said yes I have seen saltwater systems run off a bio ball run sump with filter socks and no refugium. I can say that this system the owner did more water changes then I do on any of my freshwater systems or my single salt water nano tank.
I do use bio balls in my pond filter. About once a month during the summer I clean the bio balls. This is a ~1000 gallon system with high plant growth that I very rarely have to do WC
changes on. This would probably be much more work on a salt water system with balance of minerals needed to keep the system running and keeping the ph balanced and salinity constant.
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