The pictures from Wednesday (8-10.*) were not in focus so
the count I took on them is not as accurate, but I counted
much more eggs, almost 850. I am wondering what could be
the reason for diminishing number of eggs every day...
Could it be some predation ?

It is normal that eggs dissapear through time. There are many reasons why
this happens. My guess is that not all the eggs get fertilized by males
sperm so some of them are wasted. Other eggs can get some sort of bacterial
or fungal infestations, some can be eaten by fish (not likely 'cose clowns
defend them like crazy), shrimps, worms...
More and more eggs will be lost until hatching but it is normal. That is the
reason why there are so many eggs. If only few of those eggs in nature
become adoult fish it is success for the breading pair.
If you achieve rearing to adulthoud 10 of them you should be very happy.
When you gain experience maybe you could rear more from each spawning.
Here is some articles on clownfish breading and rearing the fry
http://www.netpets.org/fish/referenc.../brdclown.html,
http://user.aol.com/cebrezzie/aquarium/CLOWNFISH.htm

Good luck and keep us posting!

Mislav