Question
why do my fish stay hidden all the time?  

Answer
Usually if fish hide, they do not feel secure.  Are they new to the pond?  Are there lots of places to hide?  This time of year, the plants aren't growing so there are fewer places to hide.  Perhaps the fish also encountered a predator like a heron, raccoon, or cat and are now scared.  To give them places to hide, add clay pots, PVC pipes, pots, etc. to the pond.

Robyn
fishpondinfo.com