help, I am losing my koi!

[stonecreek1]

Good morning all! Happy holidays! I am recently having a problem with my inside tank. The water chemistry is perfect, but I have lost several babies now and I have no idea what it is. I took a few pics today of one. It seems like it starts that I notice some white around the tail area. Then swelling. They will spend a few days in their sides. Next thing I know I find them floating. Today I noticed one or two with difficulty swimming. I quickly noticed some type of ulcer or something and appears to have the whole top of the tail gone. I am attaching pics. I am desperately seeking some advice!
Parasites?!? Infections???

 

[stonecreek1]

Here are a few more photos on another fish. Very swollen at tail base and looks like missing top half of tail!

 

[Meyer Jordan]

You state that the water chemistry is perfect. Would your please post the actual test results?
The symptoms that you describe are usually a result of a water quality issue or some other chronic stress inducer. Has anything changed in the tank recently?

 

[stonecreek1]

Sure he PH is 8
Ammonia 0
nitrite 0
Nitrate 10

Nothing has changed recently. I went through the whole fiasco at the beginning of the tank circulating and my nitrite and ammonia being high. I actually just ordered a heater because the water temp is 62 and I thought they may do better in warmer water. The filtration is running fine. Water is clear. I sweep the bottom ever few days as it is a Rubbermaid stock tank and I don't like the debris on the bottom. When I sweep it I have to add back in probably 5-10 percent water. There are a few big rocks in the bottom for them to hang. I have two air bubble pads. So I don't know. Seems I find one or two dead or starting to struggle each day. Now I did have some big (I looked this up) tobies that seemed to be aggressive with the smaller ones. I even witnessed on big one eating a dead small one! So I caught all them and removed them from the tank last week. But now that they are gone and I am still losing them I feel like it is something more.

 

[Meyer Jordan]

How long has THIS tank been set-up? Are you using a dechlorinator when you replace the 5 - 10% of water.
Sweeping the tank is a stressor for the fish.
What specie of fish do you now have in this tank? How many? And what size?
What is capacity of tank?

 

[stonecreek1]

Definitely missing tails. Here is another I found. Oh my. I am kindof freaking out!!!

 

[stonecreek1]

The tank is 300 gallons. Been set up since October. I do not use a declorinator. I have a well and it goes through the salt water softener. I have been concerned about bringing a parasite or something in from the outside pond. These guys seem to be flashing quiet a bit and rubbing against the rocks. which they have been doing before. Which in the fall we had some larger koi doing that in our 20,000 gallon pond. We didn't treat them because it turned cold and they went to the bottom before being able to do anything. So I originally caught the koi fry outside, used the pond water for start up, and grabbed several rocks, and brought them in for the winter.

 

[Meyer Jordan]

Flashing is usually a sign of parasites and Tail Rot is a fungal infection. Both are symptoms of severely stressed fish. The parasites and fungal problems can be treated, but the underlying source of the stress must be identified or problems will re-occur

I do not use a declorinator. I have a well and it goes through the salt water softener.

May be on to something here.
What is the current GH of the tank water? What is the GH of the well water before softening. Are you using Sodium Chloride or Potassium Chloride in the water softener?

 

[stonecreek1]

It is sodium chloride. And I don't have a test kit for GL. I am not sure what that is. Thank you by the way!

 

[Meyer Jordan]

GH is General Hardness. Soft water can often be a source of problems in an aquarium or pond. In addition, some Salt Water Softeners will retain a certain level of either the Sodium or Potassium ions in the finished water. Sodium has been shown to be problematic for some aquarium fish, but Potassium actually appears to have a somewhat beneficial effect.
A water hardness (GH) in the range of 100 - 250mg/L is generally recommended.
I would recommend testing the GH of both tank and well.

 

[stonecreek1]

Just got a kit and it tested at 196.5 for GH

 

[stonecreek1]

I had to use 16 drops for the water out of well. So I don't know what that is because the chart stops at 12!!!!

 

[Meyer Jordan]

Just got a kit and it tested at 196.5 for GH

Well, you obviously don't have a Soft Water problem, but you may have a problem with your Water Softener. A GH of 196.5 indicates very hard water. See chart below-

In any case, we can eliminate Soft Water as a potential cause of your issues, but if you are using Sodium Chloride you might want to switch to Potassium Chloride just to be safe.
Has there been any other major changes in the fish's environment recently? Something has obviously imparted considerable stress on them and weakened their immune response.

 

[stonecreek1]

Nothing? I was thinking the water temp since they are only and inch big might be to cold. I installed a heater yesterday to slowly try to bring it up. I can do a big water Change and add stress coat? I had three dead this am. Here is ones tail. And the other one seems to have something on its sides. It doesn't look right.

 

[stonecreek1]

Just took these two to add. I think there is possibly a parasite? Possibly brought in with the rocks I brought from the big pond? I don't know. Just desperate to help my little guys out.