Ultraviolet sterilizers and discus

by Owen James

UV can be particularly useful when breeding discus

UV can be particularly useful when breeding discus

(Image by: redvers)

Keeping discus has gone low-tech. As robust captive-bred fish have been made available, it’s become possible to keep these gorgeous freshwater fish in fairly conventional tropical community tanks, provided the discus’ needs are met.

Plants, substrate, driftwood, tetras and catfish – all things that might have worried discus keepers a generation ago – are now quite normal in discus tanks.

There are times when you still might want to go down the old ‘sterile’ route with your discus tank. If you’re breeding discus, you’ll probably have better – or at least more controllable – results in a bare tank, where it’s easier to keep the water clean and reduce the bacterial load.

For such tanks, an ultraviolet sterilizer is a potentially smart addition to your filtration armory.

You might associate ultraviolet sterilizers (UVs) with marine tanks, but in fact they’re often used in garden ponds to clear water of algae.

In a discus tank, the aim of fitting a UV sterilizer is to reduce the incidence of disease. Water passing through a properly-sized and fitted UV sterilizer will be treated by UV light in such a way as to kill bacteria, parasites and other pathogens. A UV can therefore reduce the incidence of disease in the discus aquarium.

If you’re breeding discus, the UV steriliser will have a secondary benefit of reducing the chances of the eggs being attacked by bacteria and fungus.

Don’t worry about the UV sterilizer killing the bacteria in your biological filter. It only kills bacteria that is in the water column, so the filter population is quite safe.

Here are a few more tips on UV sterilizers:

  • A small ultraviolet sterilizer costs less than an expensive discus
  • Make sure your UV sterilizer is the appropriate power for the flow of water being pumped through it
  • If you can’t turnover the tank volume through your UV steriliser at a fast enough rate (because it is too low-powered) then you won’t kill parasites sufficiently quickly to affect the incidence of disease
  • In short, buy the right UV unit for your tank size and pump rate!
  • Clean water is a must, to stop the UV light being blocked by particles
  • UV bulbs age, and need to be replaced as per the manufacturer’s instructions. You can keep pumping water over an old bulb but it won’t be effective
  • Some suggest putting the UV unit on a timer (say for eight hours a day) to reduce any risks of it changing the water chemistry. (This sounds like a myth to me, and I’ve never done it in marine tanks).
  • A UV sterilizer should not be seen as a substitute for proper filtration, water changes, and other discus essentials! It’s a back-up.

UV sterilization is one of the many controversies of discus keeping. Some highly recommend UV, others think UV is a waste of money.

Certainly UV sterilizers aren’t essential for discus, but if you have the money, a tank of expensive discus and an experimental nature, why not give one a try?

Check out Katy's Tropical Fish Guide for more aquarium info.

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