Question
MY PARENTS JUST LEFT FOR A VACATION, AND ARE LEAVING THE POND DUTIES TO ME. THE POND IS 500 GALLONS AND HAS A FLITRATION SYSTEM AND PUMP AND WATER FALL FOR CIRCULATING THE WATER. THE HAVE MANY DIFFERENT TYPES OF KOI (BUTTERFLY, JAPENESE, ETC.)ALSO GOLDFISH AND FROGS, SNAILS, AND TADPOLES. THE KOI ARE NOW EXTREMELY LARGE.  IF I HAD TO GUESS.....I WOULD SAY ABOUT 10 POUNDS.  THEY ARE ABOUT 6 YEARS OLD OR SO (NOT VERY SURE.  BEFORE THEY LEFT THEY HAD A PROBLEM WITH THE KOI DYING OFF. THE LARGEST ONES IN THE POND.  ABOUT 3 TOTAL HAD DIED.  NOW SONCE THEY HAVE BEEN GONE, ANDOTHER ( THE BIGGEST ONE) DIED.  HE WAS AT THE BOTTOM OF THE 7 FOOT DEEP AREA OF THE POND.  ALSO THE SNAIL THAT ARE IN THE POND ARE BALLS OF FUZZ.  NOW I KNOW THAT SNAILS HAVE HAIR OR FUZZ THAT GROW ON THEM....BUT THEY ARE NOTHING BUT A BALL OF FUZZ. WHEN I LOOK IN THE POND I SEE A WHITE FUZZ BALL AND IN THE MIDDLE IS A SNAIL.  ANY IDEA OF WHAT IS CAUSING THIS?  ALSO, WHAT IS CAUSING THE KOI TO DIE LEFT AND RIGHT? I WILL CHECK THE PH TODAY WHEN I GO THERE AND CHECK FOR AMMONIA LEVELS (OBVIOUSLY I WILL FIND OUT IF THAT HAS ANYTHING TO DO WITH IT) BUT OTHER THAN THAT, ARE THERE ANY REASONS WHY THIS IS HAPPENEING? OR WHAT TO RECOMMNEND TO PUT IN THE POND? ANY ADVICE WILL BE HELPFUL!  THANK YOU!

Answer
The pond is 7 feet deep!  Wow!  If it's just 500 gallons, it must not have much surface area if it's 7 feet deep.  Have you tested the water's pH, hardness, ammonia, nitrite, and oxygen levels?  I would do that.  If I had to guess, I would say that either the ammonia or nitrite levels are too high or the oxygen is too low.  Since the koi are getting large, they are too big for the pond and its bacterial population so the ammonia levels may be creeping up.  I suggest a water change with added dechlorinator and pond salt.  Also, with a low surface area, if it's warm, there may not be enough oxygen in the water.  You can add another fountain or drop an air stone in the deep end to help with that.  If your parents can have the pond enlarged, that may fix the problem if my guesses are correct.

Are the snails fuzzy white-green or white? If green, it's just algae and nothing to worry about.  If it's truly white, it may be fungus.  This indicates poor water quality.  Water changes, cleaning the filter, and adding salt should help reduce fungal populations.

So, my tips are do a water change, clean the filter, add salt, add good bacteria, test the water, and drop an air stone in the deep end.  I hope things improve!

Robyn
fishpondinfo.com