Question
I have a 150 gallon pond with koi,shobunkin and comets,2 feedings daily,chem. test is ok. appropiate filter,alomg with a spitter for circulation.Woke up to find one dead fish.if only one fish is dead,would it be water problem?any suggestions would be helpful!

Answer
Hello Frank!
One fish can be the first indicator that there is a problem, but it could also be that the fish was simply old and/or sick.
I would test the water for ammonia and nitrite, though, just to make sure. These tests are cheap and readily available and can quickly help you find a problem and resolve it.