I found it useful to be able to occasionally use mechanical filtration in the past. It's just one more means of keeping detritus down, and water quality/clarity optimal, although IMO
by no means absolutely necessary (a good skimmer will really help keep water good/clear, along w/ GAC
, etc). I like using a turkey baster to clean the rocks, etc. in my tank, followed by some mechanical filtration and a PWC
to remove as much of the stirred up detritus/debris as possible. FWIW I use mechanical filtration 24/7 now, only b/c I use a SCWD(wavemaker) on my return line, so the water needs to be free of dirt/debris to keep from jamming it.
The main disadvantages that I know of are, as said, any mechanical filtration can become a NO3
source if not cleaned regularly. Also if it is allowed to become laden w/ nitrifying bacteria and it is all removed or replaced/cleaned at once, you could see a small cycle from the loss of beneficial bacteria. Regular cleanings will help prevent this from happening as well. Some people wash mech. filters in SW
to avoid killing any beneficial bacteria.