[img]12

I think one of my fish has turned carnivorous in the pack. This is the 3 rd one found with some wounds(pictured in 1 &2). 1 was found yesterday afternoon and 1 this morning. There seems to be definite wounds on each. From the photo you can see the fins torn and still some blood in it.

Initially noticed the fish just flow with the current through the pond. The current would also swirl them around sometime in a 360degree loop.

Both were gasping for air as if they has ran marathons. Placed them in separate tanks where they eventually died after a few hours. Dont have a microscope yet, so cant do those tests. Not sure if this is a disease of some sort. Gut feel is that it is the 2 chagoi's (see black brown koi under what photos of good / bad i think) because the larger one was chasing the fish around the first time we put him in, rather aggressively.

Any opinions.
PS also have netting in place so i don't think it is anything external

Hi,

Koi doesn’t attack each other! They are one of the most nonaggressive fish in nature.
Males do chase Females around before spawning.

I think that it is a bacterial disease. As bacterial infection like Aeromonas or Flavobacterium columnare (Columnaris) can cause fin rot, gill rot and mouth rot. Both could be responsible for ulcers.

These infections can wipe-out your total collection.

A close-up photo of the infected/dead Koi will be helpful.

Koi usually dont eat each other except for when they are very little.

I have noticed on my own koi last year when one of my koi had an ulcer that some of the other fish would come and suck on the wound of an injured one...not sure if this is what you where seeng.

I have notice that other fish like gold fish, swords and neons tend to chance a sick fish around...not sure if you get the same with koi.

Pieter, attached are a few closeups. The green in the pics is the Bao Bio Wound medicine.

1. [img]2345

thnks in advance

ubhaga,

This is definitely a bacterial infection and it could be a secondary infection to a parasite attack.

You should check the following.
pH
Ammonia
Nitrite and Nitrate readings.

What is the volume of your pond?
How many fish in the pond?
Average size of the fish?
Did you ad new fish recently?

ph 6.8-7
ammonia and others all low

pond size 12.500l

Fish about 110
100 of them are 5-8 cm
5 around 10-20cm and 5 around 30cm

Bought some from the koi show 2 weeks ago. Added them in already.

Thought that it may be a bacterial infection. I add on a weekly basis bio vital powder and do 10% water changes. Also no fish are showing any signs of stress or any other symptoms.

(need to get a good microscope)

WoW!

You are OVERSTOCK!
The volume of your pond could never handle that amount of fish (125 liters per fish!)
A safe calculation would be to keep only the ten big Koi (1250 liters per fish), if there should be a power failure, I bet you will lose all your Koi.
By adding “new” fish to the pond, without being quarantined ads to your problems.
If your water parameters are correct, I will be surprised, it is nearly impossible!
The readings should be as follow:
Dissolved oxygen > min. 7-8mg/l
Free Ammonia > max. 0,02mg/l
Nitrite > max. 0,2mg/l
Nitrate >max. 50mg/l

As things are standing now, you could lose more fish!
I would suggest that you do 20% water changes per day in the meantime.