Wet Dry Filter / Trickle Filter

How Wet Dry Filters Work

A wet dry filter uses a chamber containing bio balls that are suspended above the water line, with water from the aquarium being dribbled over the bio balls. The bio balls have an enormous surface area and with the water dripping and dribbling over the bio balls the dissolved oxygen levels in the water are allot higher which allows you to grow more beneficial bacteria in a smaller space.
Step by step lets go over where the water goes in this type of filter.

Starting form the wet dry filter. Water enters the filter supplied from the aquarium (a) and flows into the first chamber (b). This chamber is designed to reduce noise from the water flow and spread the water over the drip tray (c). Inside the drip tray is a fine filter pad designed to remove particulate matter from the water, this helps keep the water clear and also keeps excessive amounts of waste from building on the bio media. The drip tray spreads out the water into uniform streams over the bio balls (d). The largest space in the trickle filter (e) is where you would place an aquarium heater, protein skimmer (if its a saltwater aquarium), and other miscellaneous items. Next the water flows through a sponge (f) and then finally into the last chamber where you would place your return pump or intake for the return pump. The return pump pumps the water up to the aquarium causing the water level to rise a bit. Water then begins to go over the overflow (g) and down through the bulk head (h) to the wet dry filter via tubing or pipe completing the cycle.
Wet Dry FilterAquarium Overflow

Choosing The Wet Dry Filter

All-Glass Aquarium Co. Mega Flow Trickle FilterThere are many different brands of wet dry filters you can choose from or you can build your own. If a wet dry filter system is new to you then purchasing a wet dry filter would probably be your best option. A manufacturer can provide you with a warranty and a quality proven design.
In this article we are going to use the All-glass Aquarium Co. mega flow sump as an example. Although there are many different brands of wet dry filters out there in my opinion the mega flow acrylic sump is the easiest to install and work with. All-glass Aquarium Co. has made the mega flow system versatile enough to use on non all-glass brand aquariums, and if you are using it with an all-glass brand aquarium it is defiantly the easiest to setup.
Wet dry filters are commonly made out of glass or acrylic. The filters made of  acrylic are the best. Acrylic is very strong, flexible and easy to drill. So if you plan on adding external pumps and protein skimmers go with acrylic.

Sizing The Wet Dry Filter

The size of filter you choose may be the most important decision you make. There are two things to be concerned with one is that the trickle filter can handle the size of aquarium in terms of biological filtration. The second is that the trickle filter can handle the overflow of the aquarium if the power goes out or the return pump stops pumping. Wet dry filter manufacturers will recommend aquarium sizes that there filters will work with. Make sure your aquarium matches the recommended volume and tank dimensions.
Example: 110 gallon aquarium can be the different measurements requiring different size wet dry filters. 48" x 18" x 29.5" and 60" x 18" x 23.5" are both very close to 110 gallons. To be safe allot of people tend to oversize the wet dry filter.