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Marine Depot's Product Information—Captive Sun Lighting

What is the proper way to handle and clean a metal halide bulb?
Metal halide bulbs should be handled with care, avoid getting fingerprints or smudges on the glass. They should be handled by the sockets as much as possible. If you touch the glass, you should clean the bulb using rubbing alcohol and a clean cloth prior to turning it on.


Can I place my lights on timers?
Your corals and fish will benefit from the consistency of using timers for the lights. The lights will always come on and shut off the same time everyday for them. Make sure that grounded timers are used and that they can handle the load of the lighting system.

Many people will use timers to help simulate a dawn to dusk effect over their aquarium. Dawn to Dusk effect is accomplished by having the actinic lights come on first, then the metal halide bulbs come on. Towards the end of the day the metal halide bulbs then shut off followed by the actinics. Most people will run the actinic lights for an hour before and an hour after the metal halide bulbs.


What is this blue film on the hood/lens/reflector of my lighting setup? Should I remove it?
The blue film is a protective coating to prevent scratching of the hood, acrylic lens or reflector. This blue film should be removed before starting up the bulbs.


How high above the water should I mount my metal halide bulbs?
The bulbs should be 6-10 inches above the water surface. This will allow for the proper dispersion of light over the tank and help to prevent water from splashing on the bulb if a shield/lens is not used.


My bulb does not come on right away and takes a long time to come on is it defective?
New bulbs will be going through a “burn-in” period and this should only last for two to four days. During the burn in period, it may take a while for the bulbs to turn on and they may turn off after initially firing. This is absolutely normal and the ballast should be left on. After a while, the bulb will fire again. After the burn in period the bulbs should fire right away for you.


What if my new metal halide bulbs will not light when I turn it on?
New metal halide bulbs have a “burn-in” period that will take a couple of days for the bulb to fire correctly. To solve this problem you will need to turn on the ballast with the bulb screwed into the mogul socket. Leave the ballast on for at least 8 hours each day for 2–4 days (even if the bulb does not turn on, or even if it turns on and off). After this time the bulb should start to light every time you turn on the ballast. Make sure that the electrical circuit that the lighting system is on has sufficient power. Having a loaded circuit may cause the lighting system to not fire or fire irregularly as it is not able to draw enough power.


Does it matter how I put the metal halide bulb into the mogul socket?
Yes. During the manufacturing of the bulb, a nipple is formed on the arc tube. The arc tube is found in the center of the metal halide bulb, inside the outer glass tube. This nipple should be facing upwards between the 10 o'clock and 2 o'clock position.


How long should I leave my metal halide lights on?
This will depend on the corals you are keeping and if you are upgrading your existing lighting. Most people will run their metal halide bulbs for 8–12 hours per day. If you are upgrading in lighting (from PC or VHO) to metal halide lighting, you will want to acclimate the corals to the new light. This can be accomplished by running the lights for shorter times for the first few weeks, gradually increasing the running time one week at a time until you reach your final photoperiod.


What if my bulb flickers and will not light properly?
New bulbs will be going through a burn in period and this should only last for two to four days. After that point the bulbs should fire right away for you. Also check to make sure the bulb is making contact with the contact in the mogul socket. To check this, turn off and unplug your ballast. Take out the bulb from the mogul socket and pull gently on the tab inside the socket. This will allow the bulb to make better contact with the socket. Screw the bulb back in, making sure the nipple is facing upwards. After the ballast has been off for 30 minutes you can try to start up the bulb again. Also, if you have the ballast plugged into an extension cord it will need to be a heavy duty cord.


My bulb and ballast are making humming noises. Is this normal?
Yes, there will be some noise coming from the ballast and bulb. The bulb will tend to hum louder when it is first turned on as it begins to light up. Once the bulb has fully lit, the humming dies down.


Why does my bulb look different than the one in the store/in my friends tank?
Due to the nature of the bulbs there is a burn in period of approximately 100 hours before bulbs begin to show their “true” color. During this time bulbs will look different than bulbs that have gone through the burn in. Once the bulbs have been properly burned in, they should look very similar to other bulbs with the same Kelvin rating. Also, there will be slight color variations between individual bulbs due production variances.


Can I change the wattage of the bulbs?
No. Using the incorrect wattage bulb and ballast combination can cause damage to the bulb, ballast and/or both. The ballasts and bulb wattages must match up.


Can I change the Kelvin rating of my 175/250/400 watt metal halide bulbs?
As long as the wattage of the bulb remains the same, you can use other Kelvin-rated bulbs. There are a few bulbs, such as the Radium 20K, AquaLine 10K and all double-ended bulbs, that require special ballasts (such as pulse-start and HQI ballasts). If you are choosing one of these bulbs, make sure you have the correct ballast for that bulb.


Do I need to use a glass/acrylic (UV) shield with metal halide bulbs?
A Metal halide bulb will produce a large amount of UV light. The outer envelope of single ended MH bulbs acts as a UV shield; blocking out harmful UV-B's and UV-C's. As long as the outer envelope is not broken, damaging UV rays will not reach your tank. Although a shield is not required, it can be helpful in preventing water from splashing on to the bulb and breaking the outer envelope.
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