All my tank koi fish constantly swim against the filter water return. As if they like to receive water current on the face. This behavior is new. Kois are bottom feeders. When everything is well they lie flat at the bottom of the tank. But since 2 weeks they all line up right below the filter water return sprinkler. They only stop this behavior temporarily when they see humain beings & when they eat.
Can this be a symptoms of some uncommon disease? I have read on the internet different aquarium fish symptoms but I have never heard of anything on consistent swimming against water current.
I have a theory for now: The fish have parasites attached to their gills & they try to get rid of them by receiving strong water stream thru their mouth. What can you guys think of?
I also think maybe put a strong
powerhead in the tank to see if they will spend their whole day staying in front of it.
By the way has anyone been to a vet clinic to treat their fish? I am thinking of doing it.
About the tank:
established filter,
ammonia nitrite=0,
pH consistently at 6.6-7.0,aeration is OK, 45USGallons stone indoor pond, no lighting system, no plants, 6 baby kois & two 9 inch adult kois.
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