Ultramarine Magazine Issue 64 JuneJuly 2017

 UV & Ozone

all pathogens passing through,
but too many are missed and
afforded an opportunity to
build up in the aquarium itself.
Some UV units incorporate
helical-shaped flow chambers,
which help to maximise the
contact time.
UV sterilisers are used exten-
sively by aquatic importers,
wholesalers and retailers be-
cause many of their aquariums
may be centralised, with lots of

tanks sharing the same water,

creating obvious implications

for the spread of disease. Some

commercial UV units use mul-

tiple bulbs arranged in series

which can eliminate virtually all

parasites after one pass, and for

centralised systems they’re im-

portant parts of the life support

systems. UV units can still be

used on ‘stand-alone’ aquari-

ums, however, but they’re not a

‘magic bullet’.

Myth-busting:

Can UV completely eliminate disease?

It’s a myth that UV can completely eradicate diseases
such as white spot from the aquarium. A steriliser can
only kill pathogens which are free-living in the aquar-
ium water (and specifically those individuals which
pass through the UV unit). Pathogens such as Crypto-
caryon with benthic stages won’t all pass through the
steriliser, and some free-swimming theronts may infect
fish if they’re not ‘zapped’ in time, and multiple passes
may be needed to affect some of the larger parasites.
However, UV can do a good job of keeping free-
swimming stages at sufficiently low levels that they
don’t challenge the fish’s immune system enough for
the pathogen to present an issue. The idea when using
UV on a single aquarium, at least, is really to reduce
the numbers of viable pathogens that the fish aren’t
overwhelmed. For ‘parasite magnets’ such as regal or
powder blue tangs, UV can be a very useful addition, at
least to the quarantine tank.

The UV unit should be placed

after some form of mechanical

filtration for optimal

performance, and the more

efficient this is, the better. This is

firstly to prevent ‘shadowing’, in

which pathogens are shielded

from the unit’s UV radiation

by solid waste particles, either

within the waste itself, or

literally hiding in its shadow.

Prefiltering is also important to

prevent fouling of the quartz

sleeve. Any deposits or build-up

of dirt will affect the ability

of the UV light to penetrate

the water – which decreases

the unit’s efficiency. To clean

the sleeves, wipe them down

with white vinegar followed

by alcohol (vodka is ideal),

and let them air dry before

replacing them, ensuring all

seal and gaskets are secure.

This should be performed at

least as often as when the bulb

is replaced, but ideally more

frequently. Most manufacturers

recommend replacing the UV

lamps every six months or so

(or 5,000 – 6,000 hours of use).

After this time, the output of

the lamps diminishes, making

the unit much less efficient.

Installation and maintenance

Commercial systems often feature multi-bulb UV units to prevent the spread of

pathogens between tanks.

For parasite-prone fish, UV can help to reduce pathogen loading and assist with
the quarantine period.

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