Zebrafish embryos

[Gong Baiwei]

I am a part-time student of Dept. of Biological Sciences, National
University of Sinagpore. I use zebrafish embryos in my 
microinjection experiment. I meet a big problem of my fish embryos.

My zebrafish embryos are breeded by 5-months old fish and seem 
OK for growing. But when I use them for injecting, I find they are 
very easy to die. If I observe them carefully under Olympus 
dissecting microscope, I find the one-to 16 -cell stage eggs are all 
very ugly, they are something not smooth on the YOLK surface 
and the cell is not clear and in good shape, but they are still alive 
and can grow to a "fish".

I do not know how to do, because I change a lot of batches of 5-
months old fish, get the same problem. And it should not be 
caused by my injecting DNA and even be injected with water, they 
will die. I had a good batches of fish before half a year, I knew what 
is a good eggs, but I use the same method to treat them. I feed 
them with frozen red worm. Only change is that last time, I change 
water frequently about 2days one time, now I clean the tanks about 
1 week on time to my new batch fish . Is it important?

Can you give me some suggestion?

baiwei