Well, you'd have to make many adjustments to a wet/dry filter to change it to a fuge, as a wet/dry filter is designed to be mostly dry, and have the water trickle/drip over the media. Therefore, a wet/dry doesn't provide as much extra water capacity as a fuge. The way a fuge works is pretty simple, once you grasp the concept of it (took me a while too...) it basically works somewhat like a wet/dry, in that there are different compartments for everything, however, a fuge is designed to hold enough water to fill it, unlike the wet/dry.
Depends on how you set it up, but here's the basic flow.
1. water exits display tank and enters fuge (either overflow box, or other sort of pump/plumbing)
2. water enters fuge in the 1st compartment, which is empty of any filter media (LR, miracle mud, sand, chaeto, etc.)
3. water flows to the 2nd compartment, where the filter media is housed.
4. water flows to the 3rd compartment, where it is then returned to the tank via pump, or gravity, depending on where you place the fuge.
You can have a protein skimmer in the 1st or 3rd department, along with some other stuff, like heaters, etc. Normally, the 2nd and 3rd compartments are divided by "baffles", which are pieces of plexiglass, placed at alternating heights (it might be easier for you to picture if you look up a fuge online). These are used to keep the filter media in the 2nd compartment, and also as housing to more bacteria (kinda like bio-balls).
Hope i didn't confuse you. i tend to babble, and when you babble, it's hard to follow sometimes. This is what i found after tons of research on fuges, so i could be wrong about some points (if i am, please point it out so i know for future reference).
They're pretty easy to build, once you get the jist. I plan on making a 10 gallon one for my 35 hex, and a 15 gallon one for my 55 FOWLR (soon to be reef), in addition to my current wet/dry system. I'm going to be using regular aquariums for the base, and using plexiglass to divide the compartments, and make the baffles out of. I'm going to use an overflow box to gravitate the water to it, and a pump to return it. (right now i have a small overflow that came with my wet/dry, but i plan on getting one of those ones that has two outputs.)
jenn
