Do UV lights work?

[Patrick M. Bodega Aquatics]

Hello everyone!

After losing 3 of my cobalt discus due to parasites, a fish shop in northern California recommended a UV light to kill future parasites. Do these work? What brand do you use? I really don't want to drop $100+ on something that isn't worth it. Also, If you don't like UV lights, what is your alternative? Thanks!

[Ken Burke]

Works for algae in the water column.  Not sure about parasites, if they pass through the uv light it should help.  

[Daniel]

Short answer is yes! They work great.

Longer answer is that they work better on some problems than others.

@Ken Burke is right, UV is good for algae, etc. in the water column. How effective UV is depends on the size and strength of the UV light and has much time the water is exposed to the light as it passes over the UV light.

It is not a silver bullet for internal parasites and it is unlikely that it would have prevented the problems you had with your discus.

UV cannot reduce pests that never pass over the UV light, for example, UV will not get rid of Blue Green Algae even though Blue Green Algae is a bacteria, because the bacteria reproduce happily in the aquarium without passing over the UV light.

[Andy's Fish Den]

Instead of a UV light, I would look into more of what the parasites were, getting a positive ID on them and treatment for them. As others above said, it will only kill parasites that are in the water column, and then it depends if the parasites spend enough time exposed to the UV light. 

[Patrick M. Bodega Aquatics]

Sounds good. Thanks!

[tolstoy21]

I use a Pentair UV sterilizer on a 125. 

The instructions on those are pretty good at outlining what flow rates you need to maintain through the sterilizer to be affective against different types of problems. As stated above, exposure time is everything, so the flow rates are much lower than what your return pump may de doing, so these may require a dedicated small pump tuned to the rate you want to achieve for effectiveness.

I will admit, that sterilizer is pricey, but it's well made.

Also, to reiterate what was said above, they only work on organisms in the water column. So internal parasites, and things in the substrate or anywhere else remain unaffected.

Edited October 1, 2020 by tolstoy21