Mr. Saltwater Tank

The Most Important Thing To Do Once You Replace Your Bulbs


When bulbs age, they lose their brightness, (called PAR) and their spectrum of color shifts. No matter how good your eyes are, you can’t see these changes.

So when you put in fresh bulbs, the new bulbs have more PAR and a different spectrum of colors.

Therefore, the MOST important thing you can do after you change your bulbs is to slowly ramp up your photo period (how long your lights are on in a day).

The first day after you change your bulbs, only leave them on for 2 hours, then every 4-5 days, add an hour, slowly building back up to your full photo period. If you see corals bleaching, or turning brown, slow down! Back off one hour and leave your lights there for a week, then add in an hour and see how your tank reacts.

(For you tank dabblers, I’ve seen fish hide all day when new bulbs are installed, so ramp up your photoperiod as well, but you can add 2 hours each day)

Why do corals react this way?

It is the reason that when you go to the beach for the first time in the summer, you burn. Your skin is not used to the bright sun, so unless you put on sunscreen, your skin burns. When you put in new bulbs that have a higher PAR rating, and a different color spectrum, your corals can’t handle the sudden exposure to this new light and they “burn” by bleaching, or turning brown.

For light bulbs in your tank, change them every 6 months, and then slowly ramp up your photo period.

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Comments for this article (5)

  • Luis says:

    If I could understand is something like this:

    Photoperiod from T5 white 8:00 to 7:00 ant T5 Blue 9:00 to 8:00

    So you are suggesting that when new bulbs are inserted that the photoperiod becomes slower like this:

    1st week 8:00 to 6:00 white 9:00 to 7:00 blue
    2nd week 8:00 to 7:00 white 9:00 to 8:00 blue

    Something like that

  • Luis…Here’s how I’d ramp up your lights:

    day 1-3: white’s on for 2 hrs, blues on for 4
    day 4-7: whites on for 4 hrs, blues on for 6
    day 8-11: whites on for 6 hrs, blues on for 8, etc, etc

  • Eduardo says:

    Hi Mark,

    In my 52 gal marine aquarium i have a 192 Watts power compact lighting system (96 Watts Daylight and 96Watts actinic). Could you tell me what must be the light photoperiod? How many hours Daylight and How many hours actinics?

    Thanks

  • Eduardo…its really up to you. I run my actinics for 12 hrs and my halides for 7 hrs.

  • hernan chaves says:

    Hi Mark, i just got my radion xr30w i had some cheep led’s the tank is about 5 months old and im not shore whats happening i lost a green frog spawn little by little started with some brown slime(in a form of a liquid sack) i deep it in coral deep rx and i thought it was because the algae maybe poor light then my metallic green alveapora excelsa got some green algae and its been dying away i deep it in some hydrogen poraxide and i put it back in the tank in a very low light area even though i have this problems of algae or bacteria witch i dont know how should i start the britness of the lights? tank is 18inchx18inchx18inch=24 gl Thanks

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