Taking lessons learned from years of saltwater keeping, I made my sump, and you can too! Not only does it, IMO, provide superior filtration, but it also increases water volume. My 90 gallon tank actually runs approx. 125 gallons of water. The larger the water volume, the longer it takes to get dirty! Materials needed: A tank (duh) size is your choice. Of course bigger is always better, but stick with what you can fit into your setup. My main tank is 90 gallons, my sump is 35. quarter inch plexiglass plastic creating (as used in flower arranging) with half inch square holes clear silicone Depending on the size of your tank, you can make it with three compartments like I did, or make only two for smaller tanks. Cut plexiglass to fit side to side of your sump. For three compartment setups you will need 2 pieces six inches wide, and 2 pieces 9 inches wide. Of course for two compartment setups you will only need 1 of each. Cut the plastic creating also long enough to touch side to side and 2 inches wide. 2 pieces for 3 compartment setups, 1 piece for 2 compartments. Measure your sump tank, dividing it into 3 equal sections, making small marks on the glass with a permanent marker. (remember, this is a hidden tank, so neatness does not count) Now on each inital mark, make longer marks 2 inches on each side of each mark. (this will create 4 inch openings for the water to flow). Starting from the left working toward the right, on the first mark put in a 6 inch piece of plexiglass, silicone it in on all 3 sides touching the tank. On the second mark, put in the precut piece of plastic create, silicone it on 3 sides touching tank, creating a one inch opening. Now put a 9 inch plexiglass piece on top of the create and silicone it in. Repeat on second set of marks, short piece first. You have now created a flow channel, over, under, over, under. As you can see, the first compartment is where the main tank water empties into the sump. It then goes over the first short partition, then down through filter floss. To do this properly you will need to cut a piece of the plastic creating 4 inches wide for the filter floss to lay on. You need to raise it off the tank bottom. To do this, take a piece of 1 inch pvc pipe cut into 2 four inch lengths, one on each end, using zip ties to attach each. Now your platform should be at the top of the opening. Why the open compartment? Should any fry be hatched in the main tank and be caught up by the filter, they become trapped in this compartment and are then able to be moved alive. The second compartment contains my protein skimmer. Not something currently common in freshwater use, but coming into it's own in certain applications. Not only does it provide another form of mechanical filtration, but by it's action, infuses air directly into the water, providing better oxygen levels, especially at night when oxygen levels tend to drop. Between the next over and under is a good place to put a media bag filled with charcoal or whatever purifying media you use. The last compartment serves double duty. It's where your water return pump is located. This is also where you can put bio balls or, as is my choice, lava rocks. I prefer lava rocks as the porous surfaces give more places for bacteria to grow. Sorry for the sideways picture. I turned it in photobucket but it's still showing this way. As you can see, instead of putting my media in a sack, I use a media reactor. Again, just a personnel choice. My return line has a T with a valve so I can divert some return water through the reactor. Last but not least, you see a float valve in the first compartment. I made an automatic topoff system. I took a 5 gallon wastecan, drilled a hole in the side near the bottom and put in a brass barbed outlet. Attaching a tube, ran it down to the float valve installed in the higher first divider. As water evaporates and the level drops, the valve allows water to trickle in. I can go for over a week without needing to top off the tank! If you have a 2 compartment sump, you can eliminate the middle section. If you want to use a protein skimmer, put it in the first compartment. 2 forms of mechanical and 2 forms of biological filtration, oxygen levels raised, increased water volume, and auto top off. I love my sump!