How do I make a water filter for a tropical fish tank ?

If you're using a large tank, you could try building a sub-tank to be held beneath the aquarium within the stand.  You can use the sub as a multi-stage filter and settling tank or a refugium.Now why would you want to build one when they are cheap enough to buyUnless your tank is very large it is way cheaper to just go buy one.I would highly reccomend just buying one, as they come with good warrenties, and efficiency, as well as being fairly cheap. Look into http://www.bigalsonline.com/?splash_done... For a filter to be made, without getting into complicated sumps, a fairly small tank is needed. Any bigger and the costs of making the filter will exceed the price of buying one. Search for an aquaclear, or maybe an eheim classic or filstar. They are fairly cheap and have an excellent reputation. Otherwise here http://www.fishforums.net/index.php?show...