clownfish spawn die

[fallnhorse]

i have a pair of mated clownfish. my tank is 4 20 gallons connected to a sump. with live rock and heavey skimming. have cheato in the refuge. my clownfish have spawn 2 times. first time took the eggs out after 8 days to a rearing tank with same temp and salinty< Never touched air>. only two hatched. next time i waited 8 days and moved the parents to another tank on the systems none hatched. they are oscillirs clownfish. they are on their 3 spawn today and i got 10 gal & 5gallon full of rotifers. how many things am i doing wrong? clowns are in tank by thhemselves SALINITY 1.023 temp 7980 ph8.1 ammo 0 nitrite0 nitrates 0 thank you also they are fertile they change to the point you see thier eyes

 

[bang guy]

Air doesn't hurt the eggs so there's something you needn't worry about.
What kills eggs is CO2 buildup. They need waterflow to remove CO2 and other waste. Also changes in water quality.
If you're going to put them in a 5 gallon tank I suggest either hanging them so they are barely underwater or setting them virtically with an airstone right next to them. This will increase gas exchange and remove the excess CO2. The parents normally fan the eggs to perform this function so if you remove the parents and don't do anything to replace the fanning then the eggs will suffocate in their own CO2 buildup.
To avoid changes in water quality, use only water from the display tank when filling the hatching tank and fill it only minutes before transferring the eggs. Move the eggs after they turn silver and before it gets dark. Make sure the hatching tank is completely dark and don't shine any light on them.

 

[fallnhorse]

i think youre right about the co2build up. i will let the parents hatch them then remove them after lights out.