I killed a fair number of fish with frozen bloodworms, before I caught on that many are unsafe. Some big name brands, here in the US, have poor quality-control at their asiatic sources. The worms sit in buckets in the hot sun and die, and they freeze them anyway despite the decay products. Some fish bloat and die quickly when fed those bad worms. Your nose may or may not be able to tell.
Stores can defrost and refreeze worms to the same end effect, but I have generally found SF Bay Brand and Hikari were safe if the packages were flat and undistorted by thawing.
You can check for Glugea yourself on a recently dead fish. Use a razor or scalpel to slit open the gut (or just squeeze out the contents) and look for white balls. The Glugea cysts are hard to miss. They look like oversize white opaque eggs. The KT archives have ways to treat for it.
Wright
01 760 872-3995
805 Valley West Circle
Bishop, CA 93514 USA
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