Do concrete ponds normally hold water? Discovered in my backyard filled with dirt! Should I seal it w something?

It is probably from the 30's - 50's and is currently filled with dirt. I am planning on digging it out, and getting it running by next year. It looks to be concrete with rocks along the top wall. It is only about 5' at the longest and 4' at the widest (roughly pear shaped), will that size be able to successfully sustain fish? (not counting fishing birds and wildlife ;) ) Thanks!! :)
  4 answers
Your comment...