hi, checking out the pond today I found my second dead fish in two days. i wasn't very concerned over the first one it was a 3 inch koi from petco. i don't buy my fish from stores like that but my son saw it and i gave in. it was around a week and a half in the pond. the second one makes me concerned. i have had this one for some time now. he was around 10 inches and one of my favorites. seemed to be eating well, was not as social as the others but seemed healthy. no ulsers, cuts, scrapes, etc. tested my water everything was good expect the salt level was low due to quite a bit of rain I assume. i am very worried for the rest of my fish. any ideas? thanks in advance.