underground filter

Question
I have a 20 gallon tank with a hanging filter and an underground filter. The Aqua Clear 30 Power Head is for the underground filter, but I don't think I have it hooked up right. This is my first tank and I am clueless. I have the underground filter in, plugged 3 of the holes and have one clear tube running up the tank. The power head is hanging on the tank and the cone thing is inside the tube. There is alot of bubbles coming out where the deflector plate is. I have nothing else. After running this a couple of weeks, I do not see or understand how this can possibly work. There is no filtration device, like charcoal or anything. I don't think that the cone part of the power head does anything. What parts am I missing and what should it really be doing? I am a visual person, so a picture would be great. I have been online searching and cant find anything to give me any idea of what to do.

Thank you!

Clueless in Salt Lake City....

Answer
Hi Alice;

The bubbles can be adjusted by twisting the tip of little valve at the end of the small tubing that sticks out of the water. It's called the "Venturi Valve". The other end connects to the powerhead at the top near the deflector. You can turn off bubbles completely if you don't like them. I personally like to see the bubbles so I know that my power head is actually working, and, well... I just like bubbles. ;-)

Your filter system is actually working perfectly fine and is operating as it should. Undergravel filtration is mostly biological so you don't need any extra stuff for it. The gravel on top of the plastic grates will serve as a home for beneficial bacteria colonies to grow on. This beneficial bacteria is what consumes your fishes' waste. The powerhead is supplying the beneficial bacteria in the gravel bed with oxygenated water to help it thrive and grow. It can't survive without it, and neither can your fish. In air pump UG systems, the air pump does the same thing. The bubbles come up through the tube, pulling water up with it. The oxygenated water is also continuously pulled down through the gravel and then up and out the tubes again. Your gravel depth must be at least 2 inches for it to be effective and provide enough bacteria bed area. If the bacteria colonies are too small, it can't be very effective. Here is a web page with info about UG systems with a small pic on the right side;

http://www.firsttankguide.net/ugf.php

Many hobbyists use an extra filter that hangs on the back or a canister that connects with hoses in addition to the undergravel. A second filter source like that is great as a backup. It also depends on what type of fish you will have or how heavily stocked your aquarium will be. If you will keep larger messier fish such as goldfish or cichlids, the UG will not be adequate. In my opinion, UG should not be used with large fish at all. They create too much waste waste for it to break down properly and toxin levels are often  continuously elevated. UGs are good for small to medium-sized community fish.

At Your Service;
Chris Robbins