While I have never kept ahaetulla, I have kept other species that are part-time piscivores.
It's imperative that if you provide a diet of feeder fish, you buy fish that do not contain thiaminase. Without going into a bunch of nerd talk, feeding prey items that contain thiaminase can result in dangeourlsy low levels of vitamin B1.
Smelt, goldfish and rosy red minnows all contain relatively high levels of thiaminase. There is a comprehensive list out there of fish that are safe to use as feeders, I just don't have the link anymore.
As far as "safe" live feeder fish go, guppies, mollies and platys are considered safe in regards to thiaminase. With regards to the diseases they carry, well.............feeder fish in fish stores are not usually kept in the best conditions........................