I have a hovabator incubator and have used this for the first time with my call ducks and australorp chickens with a staggered entry time so the eggs hatch at approximately the same time.
I filled up the 1st water pan according to instructions which gave a humidity reading of 50 - 60% on a digital hygrometer and filled every couple of days. To begin with I added the 13 duck eggs to the bottom auto turner and 7 days later added the 25 or so chicken eggs and candled the duck eggs; 8 looked good and 5 were infertile so I removed them.
On day 17 I checked all eggs, All 8 duck eggs looked good and 5 chicken eggs had blood rings and were removed. On day 24 I candled the eggs again, only 1 or possibly 2 duck eggs looked ok, all the rest of chicken eggs looked ok. I ended having success with the rest of the chicken eggs but had no duck eggs hatch :(
I'm thinking bacteria could have been an issue as the eggs were not cleaned but I would not have thought all would have gone bad as half looked spotless.
Here are some photos of some of the eggtopsies after they all failed the float test and had a high float. Please help, I really want to learn from this