Gold fish dying

Question
I have had a successful pond for 5 years with 35 goldfish.Lately each day i have come out to find tone or two goldfish dead. I have had them since the start and all would be around 6-7 inches in size.  I first noticed that they seperate themselves from all the others and are gasping for air at the top of the pond. I have recently checked the filter and waterfall and all are okay. They have no diseases on them that i have noticed.
Recently i acquired 2 new fish - cannot rememeber the name?
I also have added a large amount of tapwater to the pond but have been putting in "tapwater safe" solution to regulate it.

Could this be the problem or are they just old or is it the 2 new fish i acquired???

Many Thanks
VK.


Answer
I'm sorry that you've lost some fish.  Certainly either the new fish or the new water could be a factor.  The gasping for air may indicate low oxygen levels or a problem with their gills.  Has it been hot lately?  You can buy an oxygen test kit for under $10 and test your oxygen.  Sometimes a waterfall is not enough.  I have two waterfalls and an air stone to add oxygen to my 1800 gallon pond.

New fish should be quarantined to reduce the chance that they'll introduce parasites, bacteria, funguses, and/or viruses to the pond.  The new fish may have added something bad to the pond.  Gasping could be the end result of almost any problem. For example, gill flukes and bacterial infections make it hard for fish to breathe.

A large influx of new water can cause problems.  The "tapwater safe" should have dealt with any chlorine but the new water could be different enough in chemistry to add stress to the fish.

Have you tested your water lately?  I suggest testing for pH, hardness (GH), alkalinity (KH), ammonia, nitrite, nitrate, and oxygen if you can.  Your pH, GH, or KH may be off after the large water change.  The oxygen could be low.  High ammonia or nitrite (which rarely happens in a mature pond) would cause fish to gasp as it burns their gills.

So, you have a few things to check into.  Remember that most problems can't be seen, at least not easily, by just looking at the fish.  Your local pond club might be able to help you diagnose the problems if you contact them.  I lost 13 goldfish a few years ago with no symptoms.  All tests came out normal.  Sometimes we never find out why our fish died.  Hopefully, you can narrow down possible problems.  Consider any other changes lately specifically in the weather, runoff, temperature, etc. that could factor in.  Your 5-year-old fish are not old.  I have 10-year old goldfish but they can sometimes live 20-30 year.  Good luck!

Robyn
fishpondinfo.com