Baby blood 40 gallon tank = recipe for unhappy snake. Baby bloods are extremely shy and putting them in a giant enclosure is often the cause of going off feed. She wants to be in a tight little cage where she can feel secure. Since she's in a clear, big, spacious cage with an "open top (which is what the screen top on a 40gal equates to) she basically feels open to attack from all angles from a "predator" of any sort. Remember that young snakes pretty much operate under the mindset that anything bigger is a threat.
Time to make some modifications, which fortunately is easy to do. Get a rubbermaid shoebox w/lid, a smaller version (like the 4636 model) if she's a small baby, or a bigger box (i.e. 2220/3 gallon size) if your snake is bigger. Put 10-15 holes on each "short side" of the box for ventilation, using a soldering iron ($20 @ Radio Shack & a no-brainer to operate) to melt the holes. Keep the setup with in the shoebox VERY simple - just substrate & small water bowl. Try to make sure the water bowl isn't something she can easily flip - those small, heavier ceramic crocks often sold in pet stores work GREAT. Your substrate should be something simple, too - i.e. paper towels or newspaper. Boxes this size are too small to use mulch in since it jacks up the humidity too much, and excessive humidity is a bad thing. Humidity isn't the main thing you need to be worrying about right now. Crumple up a little extra paper for her to hide under, or give her a small hide box at one end of the shoebox. I find that those little opaque plastic plant saucers that you can get at Home Depot make great hides for baby bloods. Get one 4" in diameter & cut a little hole in one side.
Get a little digital indoor/outdoor thermometer from Walmart...I picked up a great one the other day for $10, so they're not expensive. Put the temperature probe inside the shoebox so you can keep an eye on the temps. You do not need to give the animal a basking spot right now - there's cause #2 for baby bloods going off feed - get them too hot & they don't want to eat. But it IS important to keep an eye on temperatures. You want her entire enclosure to run around 82 degrees or so...but don't get too much higher than that!
Set your snake up like this and leave her alone - let her settle in for a good week - 10 days. Give her time to get comfy in her new home & get hungry. At that point offer her a pre-killed mouse, or if you need to leave something in overnight with her, get a crawler rat - the size where the rat's eyes are just open, but it's big enough for the snake to notice and also tend to move and crawl around alot, which will also help attract the snake's attention. If you can't find the right size rat, I don't really recommend leaving a live prey item overnight with your snake, since older rodents have a bigger tendency to start chewing on snakes, or even attack them outright.
Hopefully these simple changes to your snake's enclosure will be all it takes to get her to turn back on to feeding. Good luck with your baby - can't wait to see some pics!
Kara
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"Remember the days of the old schoolyard?" - Cat Stevens