UV Twin Bulbs
UV Ultraviolet Pond Bulbs Lights and Tubes
UV Bulbs for Ponds, Twin type, single end, twin pin, Philips, Tropical Marin, Oase. Our Ultraviolet Bulbs are Tropical Marin High Grade UV GPX. The wattage of the bulb will be written on the pin end and should say 5, 9, 11 watt. ie. GPX9W or PLS9W2P
As UVs are not 100% efficient, the bacterial colonisation of a biofilter will not be affected if positioned before or after the filter, as some nitrifying filter bacteria will pass through the UV to colonise the filter. However, a UV must always be pump-fed to ensure full bulb coverage as maximum use of the UV radiation will not occur in a partially filled gravity-fed UV unit. The unit will also overheat if run partially filled.
UVs can also be fitted in centralised aquaria just after the filter to reduce any cross infection from other tanks before water is redistributed through the system. The filter (mechanical and chemical) removes particulate and dissolved organic matter, improving water clarity and UV efficiency.
Likewise, slime can build up on the quartz sleeve, reducing UV penetration within the unit. The sleeve must be cleaned regularly to maintain optimum radiation. Some more advanced units are available with a built-in meter to detect a drop in UV radiation. This indicates the need for a new bulb or a clean!
The speed of water flow also affects the efficiency of the UV unit. Flow rate can be reduced so that water spends longer under a lower watt bulb or increased in higher watt systems. The latter has been shown to have better germicidal performance with the added benefit of the faster flow reducing the build up of slime on the quartz sleeve.
During the natural life of a UV bulb, the mercury vapour within the bulb gradually becomes deposited on the interior of the bulb, darkening the glass and in extreme cases causing the glass to 'silver-up'. This solarisation reduces UV output and is an indication that the bulb is at the end of its useful life and must be replaced.