Hello. Brand new here, from Wisconsin.

So I've had my Common Garter Snake for about 8-9 months now, no problems, infact I've never had any problems with these snakes.

Currently, the snake is wandering the cage using its head to find the boundaries and obstacles. Doesn't seem to notice my movement anymore (always used to) and will occasionally flip out and thrash about the cage.

Last time it ate was 3-4 days ago, about 3 baitfish minnows. Started noticing this 2 days ago.

Possible blindness?

Probable cause 1: The water he drinks is city water, and I live about a block from the water tower, and there is noticeable residue on our dishes from when the water evaporates.

Probable cause 2: I've heard that certain species of fish will cause brain illness in snakes, can't remember which species it is, or what species of baitfish i'm feeding him. I prefer to feed him leafworms/nightcrawlers but since its been winter for about 5 months now, those are hard to come by.

Any experience or advice on this situation of mine would be greatly appreciated.

PS: Vet is not an option, just looking for info/advice.