the rock/burmese cross is not very impressive visually compared to the retic/burm cross. rocks and burmese are too similar in pattern to produce a extremely visual pattern difference in the offspring, just look at an F 1 retic/burm and you will see what I mean. I wouldn't pay 100 dollars for a rock/retic hybrid, albino rock/burms are watered down hybrids like 3/4 burm 1/4 rock and are basically worthless in my opinion. I also would think fertility would be higher in the burm/rock hybrid due to the similar breeding season, in most instances fertility in USA = retics is sept-nov, while burms are after November coinciding with the rocks fertility period. I am not a professional breeder but every time I have breed retics fertile copulation occurred in October and with burms it was in dec/jan. I have never tried to create hybrids however, but am very interested in the subject.
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Frank Roberts