Undergravel Cleanroom FFU Fan Filter have been around for quite some time but nowadays it has been receiving a lot of bad press. While there are still some enthusiasts who like the undergravel filter, a whole lot of others equate it to be a fossil that has no place in a modern fish tank. And who can fault them when you see the latest sponges, filter media and power filters that compete in the marketplace these days. But the fact is, undergravel filters are capable of doing a great filtration job "as long as they are set up properly" and that is the key phrase.
An undergravel filter consists of a raised grated platform that rests at the bottom of the aquarium. Layers of gravel is placed above the platform, forming a porous barrier between water at the top and under the platform. A tube sucks out water from beneath the platform by a pump and is pumped back into the aquarium from the top. As the water is suctioned out, water from the top is forced through the layers of gravel which filters out large waste.
There are a few factors to take note for Combination filters to function to it's maximum potential. Firstly, you need to select a platform that exactly fits the base of the aquarium. Using one that is too small will have spaces around the platform that are exposed thus not providing sufficient filtration.
The gravel in this type of filter is actually its filter media so it does require some attention too. It is better to have about 2 to 3 inches of gravel on surface of the platform, depending on the size of the aquarium and the strength of the suction. It is also ideal that you have different grades of gravel, but do not use gravel that is too small that would go through the platform because it will get into the pump and ruin it. Also, make sure that the gravel is distributed evenly. Some fish love stirring up the gravel and digging nests into them, keep them even.
Do not place too many decorations on the gravel. Remember, that's your Compact filters media and each decoration you place on it reduces the filtration space.
Just like any other filters, undergravel filters do need to be cleaned but for undergravel filters it is somewhat easier than how some people describe it to be. What you need to do is to vacuum the surface of the gravel at least once every week. Since you should be doing weekly water changes, all you would need to do is run the syphon over the gravel while you are suctioning out the water during the water changes and you would have solved the cleaning issue. Just be careful not to swish the hose around the Pleated Metal Mesh Filter too much so that you don't stir up any debris.