Undergravel filters are often considered slightly old-fashioned, but as with most things they have their place if used correctly. They work by means of a grid that sits on the bottom of the aquarium, with a layer of gravel over the top. Uplift tubes, like those on air-driven sponge filters, are attached to the grid. The filters are powered by air pumps, or powerheads, and draw water down through the gravel and into the uplift tubes to be returned to the aquarium. The gravel acts as the filter media and this is where the bacterial colony lives. These can be reasonably efficient filters but you do need to keep an eye on debris and waste accumulation in the gravel. They are not suitable for planted aquariums as the plant roots prevent water from moving freely across the plate. They are also not suitable for fish that like to dig.
Great for use in fish tanks and aquariums
You'll find lots of tubes, hoses, and accessory pieces (connectors, shut-off valves, etc.) on eBay for your , no matter what kind you have or how you have it set up. To operate an aquarium, you need to ensure that water, air, and carbon dioxide are transported constantly from one area to another. You'll need the right assortment of to make sure it is. In most cases, a few standard pieces are all you'll really need. And when you buy a new , for example, or a new , it's possible that the tubing you need will also be included in delivery. There really aren't all that many variations out there for aquarium hoses and tubing, except for differences in their dimensions. They are fairly inexpensive when sold by the yard, so you can use them to design your own hose system totally according to your unique design. The pipes and you'll need might be a different story – there are lots of different parts for the systems in your aquarium which differ depending on the type you have, and we'll go into them a bit more in this buying guide. No matter what you need for your aquarium, you can find it quickly and easily on eBay. If you want to read more about aquariums, you can also find a good selection of on the subject.
Airline Tubing & Valves for Aquariums - Drs. Foster and Smith
Almost all aquariums use a standardized tubing size of 4/6 mm (interior / exterior diameter in mm) for and . Most of them are made of PVC or silicone; silicone tubes are slightly more expensive, but retain their flexibility much longer. There are also, of course, all the accessory pieces you could need for these standard sizes hoses as well, including T-connectors, splitters, shut-off valves and check valves, so that you can use one air pump to operate multiple devices (i.e. an air filter and an air stone) or even different aquariums.
Aquarium Air Pumps: Flexible Airline Tubing by Tom Aquarium Products