Zebrafish advice

[Schofield]

I am currently undergoing a research project involving the mating of 
Leopard danios and Zebra danios and am encountering some 
difficulty maintaining the fish.  Any advise would help.  We have 
been having trouble maintaining acceptable ammonia levels, could 
you suggest any organisms that my assist in this matter.  Also, 
the fish seem to be losing some of their pigmentation and have 
gone from black or dark grey Zebras to a faded light grey or even 
tan.  What might that problem stem from?  Could it be their food 
source?   

Regards,
Elizabeth Schofield
betsys at fast.net