My mandarin used to go up and down sometimes, so I would say its pretty normal.
However, the ruby reds are even more difficult than a regular mandarin. They are actually delicate where as the normally seen blue and red ones are quite hardy. Plus they eat pods
and only pods
. Its rare for them to go to frozen food, even more rare than the reds and blues going for it.
After only two weeks I would def think about returning him or buying some bagged pods
. The sand doesnt really contain the pods
, its the rockwork that does. You ve put yourself in a very awkward position unfortunately.