Looks like this thread hasn't gotten the response that I'd expect. I'm not a saltwater guy, but I know a few things that may be enough to get the ball rolling. So, it looks like the back of your tank is a built in sump, which is a space efficient method. On the side with the overflow, the grooves that allow the water to go back there, you'd have your mechanical media, sponge basically, to remove the larger bits of debris and detritus. The water will flow through that, up the narrow portion, and those next chambers will house the fun stuff like your skimmer, heater, and biological filtration such as the bioballs. I'm not sure what other options you'd have for the biological filtration in a saltwater tank, but I know in a fresh, you can use things like ceramic media from a variety of manufacturers, or even lava rock, either of which I'd make sure is in a bag so you can pull it all out conveniently. After that, you'd have a return pump to put water back into the front part of the tank.
