This is an interesting point of view. Do you run filter rollers on your own system(s)? If not, filter socks? And if so what portion of the flow would you say makes it through the mechanical filtration as opposed to what portion bypasses it?Off the top of my head - Removal of beneficial organisms, rapid depletion of filtration media to no major benefit.
Higher propensity for clogs, floods, etc. and a single point of failure. Plumbing complications and complexity, etc.
Even if 100% of the system water is run directly into a skimmer, not 100% of the fauna (or anything else) is removed.
This is not an all or nothing thing and moreover, even you do directly process 100% of the water through mechanical filtration, you will still have detritus throughout the system. Most people who reef rollers (or socks) realize very quickly that they fill up with pounds of crap, but the system still accumulates as much crap (pun no pun) as it did without the mechanical filtration.
On this topic- Id love help from both of you @BeanAnimal and @Wave Whisperer - is there any major noteworthy advantage to setting up your emergency drain to completely bypass to the return chamber? Like, why SHOULDN'T the emergency drainage still make its way through the protein skimmer, refugium, etc.? I can see it being wise to keep the emergency pipe elevated so when its in use you can hear it and react accordingly, but why not just have it make noise into the same spillover chamber as the rest of the pipes instead of totally bypassing the system?My main drain pipe is hard plumbed to the roller and the emergency just drains down straight in my return chamber, although its raised above the water level so I will know if I encounter trouble in the main drain.