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Home » Saltwater Aquarium Supplies  » Lighting  » Light Bulbs  » Metal Halide  » Single Ended  » 250 Watt  »  20000K Metal Halide Bulb - German Radium, Mogul Base
20000K Metal Halide Bulb - German Radium, Mogul Base

20000K Metal Halide Bulb - German Radium, Mogul Base

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20000K Metal Halide Bulb - German Radium, Mogul Base Information


The German-made Radium 20000K metal halide bulb offers excellent coloration and good intensity. It is crisp-white with a strong blue tint. It brings out the fluorescent pigments in corals nicely. Fluorescent supplementation is usually not necessary, but can be used for added intensity and to simulate dawn and dusk. An electronic ballast, magnetic pulse-start ballast or magnetic HQI ballast is required to ignite this bulb. This bulb is white with a blue tint on a magnetic HQI ballast. It will burn more blue on an electronic ballast or pulse-start ballast. An excellent choice for  reef tanks 22"–30" deep.

Common questions/problems concerning metal halide lamps:
  1. Metal halide lamps of the same kind are different colors?
    Metal halide lamps operate by passing an electric arc through an arc tube that excites particles in the arc tube. When the metal particles reach an excited state they emit energy in the form of visible light. It takes 100 hours of operation before the metal particles stabilize and become a consistent color. All metal halides require 100 hours of operation before color and light output stabilize. All metal halides inherently have a slight color variation between individual lamps.
  2. The metal halide lamp fires and then either burns dull or the arc extinguishes?
    Usually the ballast and lamp are not receiving enough power. Metal halides pull a high current. Usually the problem is either there is too great a load on the circuit or the extension cords are of a small wire size and can`t handle the power needed by the ballast. Use only heavy duty extension cords and try running a ballast off a circuit from another part of the house.
  3. Do I need a cover shield between the lamp and the aquarium?
    Metal halide lamps produce a large amount of UV and also have a potential of exploding. The single ended metal halide lamps have an outer jacket which eliminates most of the UV. However, they have an inherent risk of exploding and UL requires metal halide lamps to be enclosed. On double ended lamps there is no UV shield. Double ended lamps must have a glass shield or major eye injuries including blindness may occur.
  4. Can I operate a ballast and lamp together which are designed for different wattages?
    Each wattage lamp and ballast are designed together for optimal performance and safety. If you over drive the lamp it may explode and shorten the life of the ballast and lamps. If you under drive the lamp it will also shorten the life of both components and also may explode. Do not mix different type wattages of lamps and ballasts.
NOTE: The bulb should be handled carefully. Using soft gloves is a good idea to keep finger prints off bulb. This is during installation and replacement.

*Requires HQI ballast, electronic ballast or pulse start ballasts to work properly.

Bulb Replacement Guide
Bulb Types Life of Bulb*
Normal Output Fluorescent 6-12 months
Very High Output (VHO) 6-12 months
Power Compact (PC) 9-12 months
T5 High Output (T5HO) 9-18 months
Metal Halide 9-12 months
LED (non-moonlight) ~5 years (50,000 hours)
* Manufacturer Recommendations

Manufacturer Info

Radium was founded in 1904 in Wipperfürth, situated abt. 40 km north-east from Cologne in the `Bergische Land`. Already a short time later the production of lamps with high-quality tungsten wires started here. Due to its know-how Radium advanced fast to one of the most important companies of the region and nowadays counts among one of the most experienced brand-name manufacturers of the lamp industry.
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20000K Metal Halide Bulb - German Radium, Mogul Base Reviews

Average Rating
(28 reviews)
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of 3

radium 20k bulb

Reviewers Rating Excellent!

Posted: 7/4/2013 from HOUSTON, TX UNITED STATES
4.5 5
Experience Level: Intermediate

Comments: The bulb works great and gives off great shimmer. The corals seem to like it as there is great polyp extension.

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400 Watt Radium 20K

Reviewers Rating Excellent!

Posted: 4/6/2013 from BELLINGHAM, WA UNITED STATES
5.0 5
Experience Level: Expert

Comments: The 20000K bulbs are great, a lot more light then the 250 watt bulbs, but that also comes with more heat and the chiller has to work harder. The blue tint from the bulbs make the corals pop with more color.

1 of 1 People found this review helpful, did you? Yes No

Great Customer Service

Reviewers Rating Excellent!

Posted: 4/3/2013 from VIRGINIA BEACH, VA UNITED STAT
5.0 5
Experience Level: Intermediate

Comments: Your service and follow up on my purchase was excellent. Have used these bulbs before and had downsized my tank but I am now back using these bulbs. I honestly forgot how nice they were. Thank you! I'll be back!

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not a true 20K

Reviewers Rating Below Average

Posted: 12/27/2012 from SLIDELL, LA UNITED STATES
2.0 5
Experience Level: Intermediate

Comments: Great price and good intensity but does not match up with my other bulbs.It has more of yellowish tone

0 of 2 People found this review helpful, did you? Yes No

250w Radium

Reviewers Rating Excellent!

Posted: 10/14/2011 from Port Saint Lucie, FL UNITED ST
5.0 5
Experience Level: Expert

Comments: I was running 15k for the last year so I decieded to replace these with the Radiums. I am currently running dual Galaxy ballast so the pair matched and worked perfectly. The color has surpassed my expectations with a ice blue ice white color. The only way to explain it is an artic blue/white ice color. All the yellow is removed and the colors just pop. If you are on the fence about purchasing these don't hesitate. I should have purchased these long ago. Just make sure your ballast will run this style bulb.

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Reviewers Rating Excellent!

Posted: 1/30/2011 from GRESHAM, OR UNITED STATES
5.0 5
Experience Level: Intermediate

Comments: I have a 120 gallon mixed reef aquarium. I run 2 VHO UVI, 2 250W 14000k metal halide bulbs and LED moonlighting. When I switched from the 14000k to this bulb the response from my corals was amazing! Within a few days the colors were deeper, more pronounced. MY SPS are very happy as our my soft corals. This is simply an incredible halide for my reef.

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best bulb

Reviewers Rating Excellent!

Posted: 12/11/2010 from SANTEE, CA UNITED STATES
5.0 5
Experience Level: Expert

Comments: There the best and everyone knows it. perfect color.

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DO believe the HYPE

Reviewers Rating Excellent!

Posted: 11/5/2010 from Los Anegeles, CA
5.0 5
Experience Level: Intermediate

Comments: I have 4 x 250w radiums in lumenarc reflectors driven by ice cap 250w ballasts over a 180g SPS reef with bare bottom. The colors have been awesome for the past 2 years. SPS with all colors of the spectrum. Growth is good with stags growing 4-6 inches, tables 2-3 inches a year in very high flow. Previous SPS reef had 10k ushios with PC actinics that produced very fast growth, but yellow & orange turned brown, pink/red turned orange, blue turned purple/brown - although it did have a nice dawn/dusk effect. I also used 14 hamiltons and ushios for a while but the did not make the colors "pop." The other 20k bulbs I used were very DIM. I ditched the actinics. For dawn/dusk I fire up the MH bulbs 15 minutes apart in an East-West sequence. Radium is a terrific lamp.

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20K German Radiums

Reviewers Rating Excellent!

Posted: 5/31/2010 from SAN BRUNO, CA UNITED STATES
5.0 5
Experience Level: Expert

Comments: Heard a lot of hype about these bulbs. Most of my local Fish shops switch over to these blubs for their SPS tanks. I Liked the growth and color they provided so I decided to try it on my aquarium. Within days the colors of my corals are more pronounced. Haven't had time to see witness improvements in growth but it's an excellent bulb non the less. I would recommend it to any reefer with SPS. Usually from other 20K bulbs you get a really dull fake looking actinic blue, but with the German radiums you get a nice bright blue color close to a 14K.

1 of 3 People found this review helpful, did you? Yes No

Bamm!!! Let their be LIGHT!

Reviewers Rating Excellent!

Posted: 5/21/2010 from REDFORD, MI UNITED STATES
5.0 5
Experience Level: Expert

Comments: WOW! I put (2) 400w 20K's over a 150 6'. Shut down a 5 yr old 120 4'. I brought Full Colonies over. I mean Colonies, 30-40 head LPS pieces. I was running (2) 250w (1) 175w all XMs. Within 3 hrs of turning the lights on, my LPS's were HUGE!! The star polyps don't like the bulbs right now, but they'll get used to the intesity. I am amazed with difference in mfg of bulbs. Well Worth the additional cost over any other I would of purchased.

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of 3
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