Thanks for all the info lads. LFS was selling lance fish that I was feeding them and I think that's ok, but they've changed to selling this type so I'll give it a miss just to be safe.
TBH, our fishes died for other reasons like: fish trying to "walk on carpet", big fish eat small fishes, territorial fight to dead, poor water condition, equipment failed...you can keep counting BUT fish actually died because of "thiaminase" pretty much none exist in our hobby LOL they pretty much die before food poisoning with above reasons.