1-System View

UV Sterilizer for Aquarium

Ultraviolet (UV) Sterilizers are used to control infections by stopping the spread of microorganisms from one fish to another through the water. A UV Sterilizer, when operated correctly, will kill free-floating micro-organisms with its light source. However, the UV light has no residual effect and will not kill organisms attached to fish. In a common (traditional) UV sterilizer, a germicidal fluorescent lamp produces light at a wavelength of approximately 254 nm. The water with the bacteria/algae passed over/around the lamp irradiates with this specific wavelength. As the ultraviolet light penetrates the bacteria/algae, it mutates the DNA, preventing growth and multiplication of the organism!

Killing Issues: UV Light

Now to the factors that influence the efficacy of UV sterilizers: Although in principle, UV radiation can kill
viruses, bacteria, algae, and protozoa, larger organisms such as protozoa require a higher dose of UV radiation than smaller organisms such as bacteria. With a higher-wattage light source, we can produce more UV light, but if it can’t penetrate the water, it will not be effective. And the longer the water is exposed to the UV light, the more killing power is available. Take note, these are generalities; some specific organisms may require more or less of a dose than discussed. Admittedly, these conflicts make it very difficult to provide general rules of thumb. So seek the advice of a well-known aquarist in case you are unsure about the selection of UV sterilizer for your aquarium.

Little Sterilizer: DIY Idea

A commercial UV sterilizer may be used in your aquarium; however, for smaller aquariums, the cost may make it impractical. Fortunately, you can build your own UV sterilizers with the help of generally available spare components. Presented below are the construction details of a mini UV-LED sterilizer suitable for 20- to 200-liter aquariums. The submersible-type sterilizer can wipe out algae and parasites in fresh/salt aquarium water*.

Construction of the circuit is relatively simple and can be made using a point-to-point wiring method. See the constructional drawing, schematic diagram, and components list for a deep perception of the concept. The construction procedure is as follows: First, insert the ultraviolet lamp (LED1) in its waterproof holder and fit all necessary chassis components. Next, enclose the assembly in a suitable sleeve for overall compactness. An external 5-V SMPS is recommended for the power connection. If you use a ready-made SMPS/mobile phone travel charger, its output cable can easily be soldered to the enfolded electronics.

1-System View

Constructional drawing.

If you want this sterilizer to run in line with standard internal filters/circulators (16-mm and 12-mm standard inlets and outlets), you should fine-tune the mechanical dimensions (especially the inlet and outlet diameter) of the final enclosure to suit the needs (it should be in the form of a short sleeve that can be installed on the outlet of the existing filter). Because the ultraviolet light source is located in its interior, effective sterilizing of the water flowing out of the filter is possible without any problem.

2-Schematic Diagram

Schematic Diagram

Truly, I was not satisfied with the basic version of the UV sterilizer (shown above) because of the 360-nm/500-mW UV light source used at that time. Later, I found that 280-nm high-power UV LEDs with integrated drivers are available from many Chinese vendors. See the details included below, and good luck!

Components List (as used in the prototype)

• 10 R/-W Resistor — 1
• Two-pin Screw Terminal — 1
• 5-mm/500-mW Piranha UV LED — 1
• 5-V/700-mA SMPS power supply — 1 (actually, it’s a travel adapter for a Samsung mobile phone)

280-nm High-Power UV Led with Driver

:: Specifications of the 280-nm UV LED chip:

• Wave length: 280 nm (Min: 280 nm, Max: 283 nm)
• Output power: 1,500 mW
• Forward voltage: 6.8 to 7.5 Vdc

:: Specifications of the UV LED driver:

• Input volt: 12 Vdc
• Output volt: 6.8 to 7.5 Vdc
• Output Current: 200 mA

3- Light and Driver

Acknowledgment: UV sterilizer reference courtesy — Foster & Smith, Inc.
(UV Sterilizers: Improve Bacteria and Algae Control in Your Aquarium)

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