Zebra Danio breeding! i need help.?

i am trying to breed my zebra danios. i am so lost. the first time i tryed it worked in 30 min!! i dont think the eggs got fertilized! so i tryed to mate my fish agen. nothing for the past two day. they just freak out in the mating tank and my heater just keeps turning off. i need help. also how much are sponge filters