with an under gravel filter you can suck all the crud downwards
into gravel.........
and we used to have this cool filter called a
system one
that thing was the balls... it was an extra maintenance type
but you'd slap that sucka on there and in ten minutes the water was
100% clear .... like sparkling drinking water...
friggan amazing to see... i still have it somewhere....
i think
i know this stuff cuz my ole lady worked
in a pet shop for a couple a years...
and we used to be big into fish tanks