If you're talking about the ones you can get at Petsmart, it should come in three pieces: two side-thingies and the actual divider. The side thingies usually suction cup or hook onto the sides, and they each have a slot. the divider slides into the slot, and that makes the tank, well... divided :P Sorry for the crappy explanation; hope you can understand.
Ezekiel - Butterfly DT Male
Schnappi - Blue & Green HMPK Male
Midnight - Forest Green & Blue HM Male
Yuki-Onna - Blue & Clear CT Female
Powder - White & Clear DeT Male
"Why did they search for a new singer? Marco and Tuomas could duet and if they needed the female touch Empu could wear a dress or something." - Random youtuber, on Nightwish.