Hi MissAngel,
If you wont to have a succcessful spawning you will definatly need to set them up in a seperate tank, only a 30lt tank is required.
This is what I would do....
Place in the spawning tank a heater, a thin layer of gravel or marbles, 100mm of water from the tank they're in now, a bubbler and a clump of spawning moss or spawning mops if you don't have the moss.
Set the heater 3 to 5oC below there present temp but not less than 20oC and let the tank stablise for a couple of days.
Place a pair or trio(2males to 1 female) in the tank 2 or 3 hours before sun down, they should spawn the next morning with just a little luck.
Please note as the tank has just been set up DON'T feed the adults whilel in the spawning set up.
If you can see that they have spawned, remove the adults, if your unsure remove them the afternoon of the next day.
Make sure you have food ready to feed the fry, they will eat green water, well, what its in it, and the liquid on top of a microworm culture ( this contains baby worms and yeast ).
Good luck