I can't show you a picture because it is under the gravel. Basically it is an undergravel filter like many people use on freshwater tanks, but I run it in reverse. So I pump water down the tubes to the UG filter and it goes back up through the gravel. Very few if anyone uses them anymore but when I started this tank in 1971, UG filtration was the only thing out there because salt water fish keeping started in New York the same week I started the tank.It has gone through a few modifications but the reverse UG filter is still there and has been running fine for 42 years. SPS and LPS grow nicely and all the paired fish are spawning including mandarins and blue striped pipefish. Some of the paired fish that are spawning are almost 20 years old. I don't have a sump and only dose home made calcium which is driveway ice melter and baking soda.I also run a home made skimmer. Skimmer