guppy and thiaminase

[guidofatherof5]

are minnows safe?

Dace minnows are. Most minnows sold at bait shops are not Dace, they are Flathead/fathead minnows.
The other problem with minnows is the parasite load most of them have.
With all the other safe fish(salmon, tilapia, trout) it's best to stay away from minnows in my opinion.