They are similar in the sense that they are powerhouse in the biological filtration system and have their own dependent water reservoir. These two setups is a bit more advance and a usually requires a “drilled tank”.
Wet/Dry Filter: Some hobbyist believe that the Wet/Dry Filter is the best thing on the market since it uses a combination of Bio-balls and filter media to host the “good” bacteria colony. I personally vote this as the best biological filtration system available. They are excellent for salt-water and extremely large aquariums that require heavy biological filtration. The name wet/dry comes from the fact the filter is exposed to aquarium water (wet) and air (dry). This allows ample amount of room for good bacteria colony to grow efficiently. While this option sounds very appealing, it comes with a cost…the setup may be challenging for beginners. The wet/dry filter requires plumbing and usually includes an overflow box and return pump which is part of the plumbing structure.
Here’s a standard wet/dry system in action. You can see the drain and return hose connected. With a Protein Skimmer (white column-looking device) in the “sump” area. Wet/Dry also contains small sump area as noted in the picture where you may house some equipment.
Sump tank: The sump tanks are basically additional tank sitting inside your stand. Hobbyist favors this because it hides equipment, and is more commonly seen in drilled tanks setups. Most sump tank utilizes filter media sponges/pads/socks to capture debris and could involve additional plumbing depending on the design. You can think of sump tanks as the Wet/Dry filter cousin, given that the requirements are similar. However, with these distinct characteristics:
- Sump tanks are usually larger since you can use any tank size as long as you have room.
- Does not employ bio-balls
- Different filter media setup (multiple chambers)
A Sump tank snuggled right beneath the display tank. There are three chambers and return in the center. As you can see, its a tank with baffles which divide the tank into separate sections.