ok i bought one of these fo like $20. Basically its an internal filter with a carbon chamber, and a bio sponge. we typically don't need surface area because we have live rock in the tank so i ditched the sponge, modified it so i would have a chamber for phosphate remover. This will give me an active chemical filter and be more efficient at removing chemical pollutants and phosphates.
here's what i did
first i moved the suction cups to the bottom so when i sit it in the first chamber of the nano it will be real quiet when the pump is on
i also removed the center of the bottom chambe so it can now accept 2 filter packs. the filter packs are shown in the 3rd pic
i pack one of the filter packs with carbon, the other with phosphate remover and reattach the filter together. Then i measure the height and distance from the side of the tank to drill a hole in the back of the filter wall.
cut and insert the black attachment in the hole, drop the filter into the chamber and connect. This is all you see in the tank even though ther is an active filter in the tank.
heres a pic of the filter as it sits in the first chamber attached to that black pipe and there is almost no equipment shown in the display because it's a;; behind the wall.