ages ago i have done this on a 2 foot silver.
twice actually
first time:
ate it, took 10 minutes to swallow.
aro was happy
next day the entire surface was covered in fur (its ok if you have overflow, at the time i didnt)
and the aro was a happy chappy! no problems. In facdt some say, gut load the mouse, feed it fish food for 3 to 5 days, then wash it and feed. has so much protein and in the wild, Aros DO eat mice! because mice do venture into the water accidentally from trees, even small birds and baby water birds... it is nature, they can digest it
but the second time:
mouse was bigger, took ages to swallow and next day, spat out a half digested mouse