[Zephyr]

Today, in Honor's Chemistry, we began studying the amine group of carbons.
From what I understand, THIS is the story of thiamine.
The snake swallows the fish *let's use goldfish for example,* and as its being digested, the cells rupture in the fish, allowing the protein in the fish's cells to be turned into thiamine, which the snake would in turn use for muscle growth, seeing as the amines are basically broken down proteins. However, the thiaminase present in the goldfishs cells decomposes the thiamine into smaller pieces that CANNOT be re-formed into proteins by the snake.
So, the reason why the young snakes would be affected by thiaminase the most is because they are growing and the muscles need protein, seeing as they are made of protein. The muscle convulsions before death would be from the muscles attempting to do normal activities without protein.

So, I conclude that this would mean, if you were using a diet entirely of goldfish, you'd have to feed the snake almost daily to make sure it was getting proper protein, but this is, obviously, untested.
If rosies have less thiaminase than goldfish, then it is safe to say that, once again, a varied diet would be suitable if rosies are a staple. It may actually be safe to feed goldfish to adult garter snakes, seeing as their body isn't growing as much as a baby snakes would be. This would also explain sschind's story.