When choosing the correct UV for an aquarium there are two main things to consider,

• Tank turnover through the UV
• Water flow rate and contact time required.

For a reef tank we generally suggest turning the tank over 1-2 times per hour and 2-4 times an hour for a fish only system.

For example, on a 400L reef tank you would want 400-800 Litres per hour passing through the UV.

The speed that water passes through the UV will effect the contact time and exposure of the water to UV. If the water flow rate is towards the bottom end of the flow rating for the unit it will be most useful for parasite control, towards the top end it will be less effective on parasites but will still work well for water clarity.

Using the same example as above and the information below. A 400L reef tank would want a flow rate of 400-800 Litres per hour, so for parasite control the 20w UV with a flow rate of 500-600 litres per hour would be ideal.

10W Model flow rate: 500 l/h max 230 l/h min

20W Model flow rate: 1000 l/h max 460 l/h min

39W Model flow rate: 2000 l/h max 920 l/h min

80W Model flow rate: 4000 l/h max 1830 l/h min

(Max flow rate will give an approximate exposure of 35,000 microwatt's/sec/sq.cm. min flow rate will give approximately 70,000 microwatt's/sec/sq.cm.)

Please be aware that when choosing the pump to run the UV the actual pump flow rate should be calculated not the max flow rating listed on the pump.