Clear water with low microbiological contamination thanks to UV-C water clarifiers

UV-C water clarifiers offer you the opportunity to clear white and green water cloudiness, using a physical process without the need for liquid chemicals. Moreover, it has also the property to efficiently reduce the germ count (e.g. pathogens).

How does a UV-C water clarifier work?

UV-C radiation is the radiation range between 200 and 280 nm, which lies below the UV-A and UV-B radiation and is not visible to the human eye. UV-C radiation has a germicidal effect and therefore is used for the clarification of water. The water flows with medium speed along the lamp which emits UV-C radiation. During the contact time in the UV-C radiation germs and floating algae are killed. The JBL ProCristal UV-C PROCRISTAL water clarifier has been designed so that the thickness of the water layer and the bulb efficiency give you perfect results. To optimise performance, the pump flow rate must precisely match the size of the UV-C clarifier.

Reducing the germ count

Alongside clearing green water (floating algae) UV-C clarifiers are often used to reduce the germ load in aquarium water. Passing the UV-C bulb, all germs are killed off and caught by the downstream filter. Here you also need to be careful that the pump performance is adapted to the purpose and performance of the water clarifier (see table).


JBL ProCristal UV-C PROCRISTAL water clarifier contain an internal glass cylinder which needs to be cleaned twice a year. This is not complicated and can be easily be carried out by people who are good with their hands. It only takes a few minutes to unscrew the unit. Care should be taken when using a device with plastic inserts not to scratch them.

Replacing the UV-C bulbs

After about 6000-8000 h (often after about one year) the UV-C effect of the bulb decreases considerably and with it its clarifying and germicidal effect. You then need to change the bulb. You can easily do this yourself. Just open the housing and unclip the bulb from its fixture. Put in the new bulb without touching its glass surface (use cloth or paper). Put both halves of the housing together again – that’s it! JBL offers you high-quality JBL Replacement lamp UV-C from 5 up to 55 W.

Increasing the performance

If you want to get a larger aquarium or if you just need a higher output for your UV-C water clarifier, you can connect up to 2 units together. For that purpose, JBL provides you with a special connection piece: JBL PROCRISTAL UV-C QuickConnect .

Installing the UV-C device in front of or behind the filter?

Ideally install a UV-C water clarifier IN FRONT of the filter. Then the downstream filter can catch the dead germs and algae and they can be completely removed from the water the next time you clean your filter.

But if your filter is new or has recently been cleaned the UV-C water clarifier would obstruct or delay the biological settlement of your filter. In this case it would be useful to connect the clarifier for three weeks BEHIND and afterwards IN FRONT of the filter.

Is your water crystal-clear or t cloudy? What kind of cloudiness is it?

1. Green water cloudiness

Green water cloudiness occurs through green floating algae which can form through light and the nutrients nitrate and phosphate (for more details, see Water values ) available in the water. They are NOT harmful for your aquarium dwellers but look unsightly. With the help of a UV-C water clarifier you can safely kill off the floating algae within 12-48 h to get your water crystal clear again. As prevention measure you should use a phosphate remover ( JBL PhosEX ultra ) in future, so that subsequent algae generations have not enough nutrients to survive.

In case of green water please make sure that your water is well aerated during the NIGHT because high quantities of algae drastically reduce the oxygen content at night!

2. Whitish cloudiness

Whitish cloudiness occurs due to bacterial mass reproduction. This is not necessarily a problem but it often leads to oxygen deficiency when lots of bacteria consume enormous amounts of oxygen. With the help of a UV-C water clarifier you can safely kill off the bacterial mass within 12-48 h to get your water crystal clear again. You haven’t necessarily done anything wrong! Bacterial reproduction can happen unexpectedly and often without any comprehensible cause.

3. Brownish cloudiness

Brownish water cloudiness rarely occurs and shouldn’t be confused with brownish discolouration! Cloudiness means that you can’t look through your water anymore. Brownish water can be perfectly clear, such as the natural blackwater (e.g. Rio Negro). A brownish cloudiness mostly develops through small wood parts, gnawed off from their roots by catfish. In this case NO UV-C clarifier can help but only an extra fine filtering with JBL Symec micro or the replacement of your roots with harder wood (e.g. mangrove or bog wood).

4. Yellowish water colouring

Through fish excrement the water acquires a yellowish tinge in the course of time. You can prevent this colouring with a regular partial water change ( Water change every second week. With activated carbon ( JBL Carbomec activ & JBL Carbomec ultra ) you can remove the yellow colouring but without having combatted the cause. The water mentioned change ( Water change ) is the best measure! A UV-C water clarifier does NOT help!

5. Blue coloured water

A blue water colouring can only occur through medications which contain colouring, such as methylene blue. Normally the colouring fades after a couple of days since light destroys the colouring. After the treatment the remaining medication needs to be removed with activated carbon ( JBL Carbomec activ & JBL Carbomec ultra ). A UV-C water clarifier does NOT help!

6. Brown coloured water

Brown coloured water occurs through peat, wood or adding of so-called blackwater conditioners. Generally a slight brown colouring is desired since it resembles the natural blackwater of quite a few tropical ornamental fish and it also is very good for preventing unwanted algae formation. If a brown colouration is unwanted, activated carbon ( JBL Carbomec activ & JBL Carbomec ultra ) will help. A UV-C water clarifier does NOT help!

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