Can I catch minnows?

[KITKAT]

is there thiamin suplement in Reptivite? can other snake food suplements be used to avoid a problem?

Supplements will not solve the problem. Thiaminase DESTROYS the thiamin that the snake eats...

But a good variety of foods will prevent this. Safe species of fish includes trout, salmon, and some other species that are easy to get at your grocery. Earthworms are an acceptable food, but your snake's stools will be watery and harder to clean up after. Strips of meat such as heart, can be lightly scented with fish, and your snake will learn to accept this. Frozen and thawed pinkie mice can be scented as well, and offer very good nutrition.

Minnows should be a rare treat, IMHO.