My dwarf gouramis had built bubblenests 2 times, but the eggs never hatch and I cant find the problem :-(. Please someone help me! Thanks

Hi All. Im Trying To Hatch Around 20 Killifish Eggs. (nigerianus masaje gold) I put them In For Hatching Around 11pm GMT lastnight And it is now 1pm GMT next day. Is It normal that none have hatched yet? Also any additional Advice on the hatching process i.e What to look for, temperature etc...