Steriliser or clarifier?
UV units for pond use tend to be clarifiers. These affect the
free-floating algae causing ‘green water’, causing them to clump
(flocculate) for removal by mechanical filtration. Whilst similar
in design as UV sterilisers the void spaces of pond units may be
different to those of aquarium UV sterilisers, and the recommended
flow rates may be different (clarifiers tend to permit much greater
flow rates than sterilisers). Therefore, their germicidal action can be
very limited on the aquarium. In short, you’re looking for a steriliser
rather than a clarifier. Some UV units are designed to be run as
either clarifiers or sterilisers, but different flow rates are usually
required depending on how they’re being run.UV and the reef aquarium
UV sterilisation really comes into its own on fish-only systems, and
for centralised systems and quarantine tanks it’s a useful tool for
helping limit the spread of disease and reducing viable pathogens.
For the reef, many aquarists of wary of using UV, however, as it may
harm natural plankton populations.
Many of the beneficial copepods and other microfauna in the reef
are actually of the substrate-hugging benthic type, so a UV won’t
have much impact on their numbers, but it could affect smaller
phyto- and zooplanktonic organisms that are more pelagic in
nature. Probiotic systems utilising liquid-based carbon dosing
(vodka, vinegar or proprietary additives) rely on encouraging
heterotrophic bacterial to proliferate before being skimmed out
and in such systems, UV sterilisation potentially disrupts this
process.Myth-busting:
UV affects filter bacteriaUV sterilisers have no effect on filter or live rock mi-
croorganisms. Aquarium UV units are only capable of
destroying organisms passing through the contact
chamber, so only free-living microorganisms will be
‘zapped’. The filter bacteria are substrate-bound, so
these will be perfectly safe. However, those running
probiotic systems may want to consider if UV is appro-
priate.UV-C radiation is dangerous to our
eyesight; for the love of all that is
holy, never look at an exposed
germicidal UV lamp in operation!
Some units emit a glow of UV
light through the end caps – this is
perfectly safe. The end caps filter
out harmful rays, but give a visualindicator that the unit is running.
Prefiltering is important to reduce fouling on the UV unit’s quartz sleeve.Ensure all seals and ‘O’ rings are in place before reassembling the UV unit.