Jen,
I don't know whether you've already tried this, but I've just trawled through all ( yes,all ) the hotel reviews on the Paraiso on H.T.
There are two consecutive posts from July 2004 which mention the 100 euro deposit, but no other mention either before or after this date. Do you think that this may have been a " try-on" by the hotel which resulted in too much stress for the reception staff and was, therefore, abandoned?
From other posts it does seem that the hotel is " deposit - minded ", as there are references to deposits for golf clubs, swimming caps and even remote controls for the air conditioning !!