a few dead fish - old age???

[Shadow Darner]

Hello kda124...hang in there!

According to my calculations, and assuming your pond volume is indeed 2000 gallons, the 40 pounds of salt added raised your salt level to 0.25%.  Your first 15% water change will bring that number down to 0.21%, your second 15% change will bring it to 0.18%, your third will lower it to 0.15% (this is the concentration considered to be the threshold of supercooling).  Your fourth 15% water change will lower the salt concentration to 0.13%, your fifth (and do complete all five changes!) should bring it into a safer range of 0.11%.  This should also do wonders for your detectable ammonia...and your water in general.

If you do not currently own a salt meter I urge you to purchase one.  It is a tool you will need to use again and again in the koi keeping hobby.

Good luck...and kind regards!

Nancy

[kda124]

Here's a pic of one of the last fish to die during that spell.  I didn't spot any visible abnormalities, but maybe someone else can??
Thanks

[Lotusman]

kda124,
External exams during a necropsy often reveal nothing. Doing a full necropsy is pointless, unless you have taken a wet lab course to get some training. However, even without training, you can cut off the operculum (gill covers) to do a thorough visual inspection of the gills. Use a strong pair of scissors to do the job, and a little LED flashlight to illuminate the exposed gills. Taking note of the appearance will tell you many things. You are looking for anomalies such as; poor color, spots, missing tissue, eroded edges, slime, and even parasites if you place a snip under a scope. The more gills you look at, the better an evaluation you can do. Visual inspection of the gills on survivors can be done with (surgical) gloved hands and a LED flashlight. Inserting a finger to lift the operculum helps during this procedure.

Hope this helps.