lookin at tanks

[WookiellMonster]

Ok so i was lookin at tanks when i went to the lfs and in all of them i saw have like a black kinda canister lookin thing in the back umm hmm ok i drew a picture its not very good but hopefully you will get what im try to say... yea so what is it?

http/img.photobucket.com/albums/v229/wookiexmonster/1.jpg

 

[pseud]

 

[Jason213]

This is a Built in Overflow for incresed filtration and water circulation

 

[Jason213]

*Edit* oops, posted twice.......

 

[WookiellMonster]

oooh coool.. does it work good?