EHEIM reeflexUV and UV+e UV-C steriliser for aquariums

Each model has two flow limits, and it is this pair that determines how you set your pump. Against a haze of algae or bacteria, the 350 accepts up to 400 litres per hour and the 2000 up to 3,000. Against germs and parasites at the infectious stage, these limits are halved, to 200 litres per hour on the 350 and 1,500 on the 2000. Water that passes more slowly stays longer under the radiation, and it is this contact time that separates clarifying from disinfecting. So you set the flow according to the result you are after.

Take a 600-litre tank fitted with an external filter pushing out 1,000 litres per hour, with a reeflexUV 800. Against green water, this flow stays below the ceiling of 1,200 litres per hour, and all the filter's water can pass through the unit. Against germs, the ceiling drops to 600 litres per hour: you then pass only part of the flow, by placing the unit on a bypass fitted with a tee and a valve, which lets you adjust the share of water sent past the tube. The rest of the flow returns to the tank untreated, and the equivalent of the tank's volume still passes in front of the lamp every hour.

Models 500, 800, 1500 and 2000 are also available in the reeflexUV+e version. The tube and the water treatment are identical, and the housing adds a Wi-Fi connection that lets you control the unit from a phone, tablet or computer. You can set run periods and pauses, and a boosted mode for periods of high parasite pressure. The 350 has no controllable equivalent. From one version to the other, only the way the unit is controlled changes.

In aquaponics, the question that keeps coming up concerns the biofilter: can a device that destroys bacteria coexist with your system, which lives off them? The radiation only reaches what floats freely in the current, and the colonies attached to the filter media and in the grow medium do not pass in front of the tube. The nitrogen cycle therefore carries on while the water clears. Place the device on the return, after mechanical and biological filtration, so that it treats water already cleared of its particles.

Iron additions call for particular care. Chelated iron is photodegradable: UV radiation breaks the bond between the iron and its chelating agent, and the released iron precipitates before reaching the roots. If you add 11% DTPA chelated iron, switch the unit off for 6 to 12 hours after each addition, long enough for the plants to take up the iron, then switch it back on. The app-controlled version lets you schedule this pause from your phone instead of unplugging the unit.

The box contains the unit with its UV-C tube already fitted, its mounting bracket and screws, the ballast with its power cable, and 4 connection nozzles, two for 12/16 mm pipe and two for 16/22 mm pipe. No mounting position or flow direction is imposed, which lets you fix the bracket however the cabinet allows. The water pressure must not exceed 0.8 bar, so the unit is placed on the outlet of a filter or a circulation pump. A double quick-connect valve on each side then lets you take it out of the line without draining the pipes, so you can clean the glass tube at least every 3 months or replace the UV-C tube after 8,000 hours of running.