Simply Koi and More Koi

Last spring I had several koi which had dry skin/reduced mucus and felt rough to the touch. I never really got to the bottom of it. Although after scoping and nothing was found . I treated the pond with PP and combat antibacterial( Just incase it was costia or chilidonella or bacterial) The next 5 months and the condition of the koi improved. This spring I have found one ailing koi but is still swimming around and eating. After giving her a salt bath she has much improved, however one fin is on occation clamped. Upon inspecting the fin I have found no visible damage, however the skin once again feels rough.( possibly due to recent salt bath one week ago) I have done another scrape and again nothing was found.Several other scrapes have been carried out on other koi and also nothing has been found.The skin on the other koi is not rough but mucus is a bit on the thin side.
I have since got thinking about this rough skin and this has come about since stopping my RO system.or I did not notice it whilst it was running. I am now wondering if there is something in the supply water such as metals and is not being removed by ordinary carbon purifiers.Interestingling before running RO I did not have any problems but did run my pond with elevated K.H and G.H. and therefore any metals in the water would not affect the koi.Any thoughts would be appreciated. Best Regards Dave
P.S I forgot to mention I am currently changing water 24/7 about 5% per day. TDS 75ppm K.H. 1.5d.h G.H 3.5 d.h

Hi Dave,

Sounds an interesting one could be a brain teaser

OK so no little critters have been found on any scrapes and all water checks out for the normal stuff ammonia and nitrate and PH have you ever tested for anything else ?

What temperature did you run through winter as we are sort of just getting going as there has been some funny weather getting warmer and colder thats why i have only just removed my cover. Could it be they are just a bit off sorts from the funny weather and all the rain but as you say strange the change from the RO so first thoughts would be something in the source water could be off but its only a couple of the fish.

Is it the same fish that you had with the rough skin last year ?

Gazza wrote:Hi Dave,

Sounds an interesting one could be a brain teaser

OK so no little critters have been found on any scrapes and all water checks out for the normal stuff ammonia and nitrate and PH have you ever tested for anything else ?

What temperature did you run through winter as we are sort of just getting going as there has been some funny weather getting warmer and colder thats why i have only just removed my cover. Could it be they are just a bit off sorts from the funny weather and all the rain but as you say strange the change from the RO so first thoughts would be something in the source water could be off but its only a couple of the fish.

Is it the same fish that you had with the rough skin last year ?

gazza Thanks for the quick reply
All water checks work out fine. It is a while since I tested for copper but always zero. This is one of the several koi which felt a bit rough last year. This is the one I mentioned a few weeks ago. Pond is sitting at a nice 17 degs C so don,t think its the weather. Although we have had record amounts of rain. One thing I did forget was a 0.4 deg p.H swing, but would not think this would cause dry skin. I have really been scratching my head as apart from this the koi look in superb condition but worry about the lack of mucus. You know Gazza if it was not for the ailing koi a few weeks ago and looking deeper into it I would not know any better and think eveything is ok.
I do think about the p.H swing of 0.4 but even though I have zero growth of blanketweed on the pond walls and the UVs are evedently doing a great job of keeping the water crystal clear. I still get the 0.4 p.H swiing. This was one of the reasons why I fitted the RO to try and get the G.H lower than the K.H. But the swing was still there. Has always been there since removing the liquatha from my homemade shower. Dreadfull stuff in my opinion kept blocking up with crap and always needed cleaning.If I add bicarb it just raises the p.H away from where I want it. At the moment 7.2 to 7.6. If I keep adding the bicarb it will eventually peg it at 8.3 but do I rally want my p.H that high? Might be the only way. Strange stuff this water
I kept my pond at 12 deg C throughout winter