help

[fish meat]

i dont realy know much about cannister filter, but i heard that it is fed by gravity? then gets pumped out. how is that? the water in my tank is about 5" below the top of the tank. how will a cannister work on my tank?

how often should i change the filter (not a cannister)

please help. thank you

 

[BIGgourami]

i assume it starts a vacuum and sucks the water in.

whay brand is it? HOB? submersable? what?