Purpose of Filter

Question
What is the main purpose/reason of using filter in the equarium?

Answer
Zaigham,                                                               Without the mechanical filtration on you tank you won't be able to remove the solid wastes........ not only that carbon absorbs the toxins your fish puts or their wastes without it you could not have a successful ecosystem. Though there are some exceptions... Like female betta fish(so you can have more than one) and white clouds, african dwarf frogs, snails and corys.... These are all fish that can acclimate to tanks without heat and you do not have to build an ecosystem. You can just break down the whole tank when it needs to be cleaned and just fill it as close to the temp they are in with a little dechlorinator if you have city water and plop them back in. No filter necesary as long as you keep it clean....Good Luck,Tina