Well they are different things. A tidepool has biological filtration and a sump alone does not. A tidepool, if it is like mine at least, has an area that would be considered a "sump" where I have my skimmer and return pump. Not a lot of room but ya know, workable. If I could I would probably do some combination of wet/dry, sump and refugium. But at the moment this works quite nicely indeed :yes: So depends on a lot of factors - your fish load, type of fish, other biofilter (LR, LS, etc).