Uv And Mystery Ilness

[paul fitz]

A couple of weeks ago I noticed that some of my koi were lying on the bottom of the pond and generally not themselves. I could not work out what was wrong. Then a few days later I realised my uv bulb had stopped working, alerted by the water going murky. I replaced it, and now 2 weeks later all the fish are back to normal. I have heard, but dont know if its true, that fish that live in water filtered with uv have a weaker immune system. could their behaviour have been the effect of the uv not working?

[FishGirl-Seattle]

I used to use UV in a tropical tank and never saw anything like that when I stopped using it. Was it the UV that was broken or was the whole filter system broken?

[paul fitz]

Just The Uv

[FishGirl-Seattle]

I guess it's possible there is a pathogen in your pond that is being kept in check by the UV. But if your filter system is adequate the UV should be killing all of it - so maybe there is a pathogen that is regularly introduced into the pond. Are you on a septic system or near a farm? Did you have any minor flooding or discover any new amphibian populations in your pond prior to discovering the broken UV?

[Suzu]

I hope no one minds a beginner butting into a thread to ask a question, but if you do, please just ignore this post.... With no prior knowledge about this matter, I am wondering why a pond - assuming it is called a "pond" because it's outdoors - needs artificial UV light. Doesn't the sun supply whatever the fish may need?

[paul fitz]

direct sunlight causes the water to go green. then of course you cant see your fish. so a uv light fiited as part of your filter system keeps the water crystal clear. Hope that helps:ssmile: