Help regarding UV sterilizer

[Ascelin]

Hello
I just wanted to ask if UV sterilizers can cause damage to freshwater fish?
i have been using a submersible UV sterilizer for a few years now and it has always worked fine for me. But recently my 50G aquarium had an algae bloom so i put the sterilizer from my fish pond into the tank for a few days. The water cleared fast but some of my fish ended up lying at the bottom of the tank. They are Silver Dollars and this was not the first time i used UV in their tank. They have some scale peeling off but overall they seem fine. Their eyes are also still clear and not clouded at all. I've treated them with some aquarium salt and most have recovered already, only 2 of them still lying on the aquarium floor and not moving

 

[kendragon]

Using a UV to clear green may be masking an underlying water quality issue. Try to figure out why the water went green....lack of filtration, lack of water change, over feeding...????.
To answer your question, no an UV sterilizer should not harm your fish if everything about your tank is good. Check to see if this pond UV is heating the water too much in this 50G.

 

[monkeybike]

I'd check that it's not leaking voltage into the tank as well

 

[duanes]

The UV light only works on algae, microbes or tiny animals that pass thru it, and only if it passes thru the unit slow enough to do damage. I doubt your fish were small enough to pass thru the unit.
I would agree with the others, you may want to check for stray voltage, and check the water quality issue that brought on the algal bloom. They (not always)can be related to a lack water changes, that cause high nitrate.