Does anyone know how?

[dino_eel]

I need to either construct some sort of filtration unit or buy one, it will be used in a 45 gallon tank, does anyone know how to construct one? Is it cheaper to make one or buy one?

 

[Anglerman]

Just buy one, unless you have plenty of time on your hands. It might be some work building an efficient system.

 

[mooman]

Unless your going make sponge filters in bulk, then it will probably be cheaper to buy one. with that said, all you really need to have an "efficient" filter system is have 8-10 X the total volume of your aquarium passing through a large enough amount of sufficiently pourous material (all a filter is really). Google "DIY sponge filter". You should get a ton of hits. For a larger tank try: "DIY wet/dry fitler"