Just a suggestion, but I would not even try to feed fish to a garter currently eating mice...o.k., I should clarify that...I would never try that again. I have a large 4' that had been taking adult mice once or twice a week, until the local pet store ran out of mice, so rather than put off feeding for a week, I decided to try fish. Big mistake, now he refuses any mice (frozen or pre-killed) and won't even get close to them even if they are completely covered in fish guts, etc. and totally scented. What I'm trying to say is that if you have a good thing going, I wouldn't change it.