Hi, This is my first post here so hopefully I get things right and someone is able to help me out.

I have a Koi which is acting strange but below is teh questionairre completed to the best of my ability:
-How long has the pond been set up? 10 years or more
-Water test readings:
--Ammonia:1.0
--Nitrite:0.0
--Nitrate:0.0
--pH:8.5 Broad range
--KH (=Alkalinity):?
--GH:?
--02:?
--Salt:none
-Water Temperature:?
-Concrete, Liner, does it have a Rock Bottom?:Liner
-What kind of filtration:Large sponge type filter in undersoil container
-Water conditioner/dechlor used(brand):None
-Routine Pond maintenance: ( Pond filter cleaned every two weeks, and at teh same time water replenished )
-Source (Tap or Well):Tap
-Water softening unit?No
-What, how much and how often do you feed your fish?Dailey floating sticks and small handful
-Size of Pond? (gallons or LxWxD):7000gal
-Pond inhabitants;How many total, type and Size:12 in total. 2 large Koi and 9 smaller goldfish
-New fish or plants added to the Pond?No new fish, recently added some new plants
A: What type and when?Not sure of name of plants
B: Were they quarantined:N/A
-Medications used:none
-Describe what problems you are seeing:I have a koi that has been very lethargic recently (last few weeks or so) and it started to wedge itself behind the pump pipe and lay there all day. It is not feeding. Then today it has left this area and started to thrash about with its head pointing downwards and tail in the air. It also seems to be unable to stay upright in the normal position and starts to lean over to one side. There is what I believe to be an ulcer on the back of the fish at the juntion of the tail fin and back (see picture 'Tail' below), also it has some white marks on the side (see picture 'Side' below)
I hope youi are able to help.
There was a lot of blanket weed in the pond recently which seems to have disintegrated over the last two weeks (I have not treated this with anything it happened naturally). Now the pond has quite a lot of floating blanket weed in smal bits not the long stringy lengths.

sorry for the long post but hope I have provided enough information for someo to help - thanks in advance.

from the looks of it it is a start of an ulcer thou it is not red and angry you could try a salt bath to help and if that fails you would have to get a ulcer treatment kit for around £15 from a supplier. hope this helps

Hi ossie welcome to the forum

You say there was a lot of blanket weed in the pond recently i would treat with Eco gold has i see your PH is a little high did i read right 7000gal 12fish

like koimaster said i would try a salt bath first. can you put some pics on of your pond and setup