| actually, i had good luck getting one from an ebay company... works really well on my 55, my only complaint is that its just a litttleee bit big, and if you use the sponge on the outflow tube it backs the flow up and makes it less effecient, check out ebay express, i believe the company was catfish lighting supplies, for $50 i really don't think you can beat it...
however don't take my word as gospel, i have only had experience with one other skimmer, a seaclone 100... which was not very good.
My skimmer has flow/water level adjustment, and air adjustments, comes with sponges for intake, and out, but like I said better off leaving the outflow sponge off, makes a nice thick nasty dark green goo
you can also set it up for hang on, or in sump |