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Coral Vue Hydros

MH washing out colors?


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I have a 40 gallon tank that has been set up for about two months now. I've transferred some corals over from other tanks, and they have gradually seemed to lose color in this tank. The tanks they've come from all have 50/50 PC combinations (mostly a 15 gallon long with a 55w 10,000k, and a 55w actinic). The 40 gallon tank has a 10,000k MH, with no actinics yet. It isn't just a matter of the lack of actinics either, because when I first put the corals in under the MH they still have their color, but it gradually fades. For instance, I put a frag rock of purple zoos in and they have gradually (over a couple weeks) "faded" to a brownish color. SG, PH, temp, etc. are all good and the same in all my tanks, and the same salt is used. The only difference is the lighting. I've placed the transferred corals low in the tank to acclimate them to the higher intensity light and they still lose color. Any ideas?:(

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doooooooooood your corals need to adjust to the lighting! How long are you running the MH per day?


1. Do not place any corals too high (which you havent...good)

2. Turn the lighting period down to 2hrs max!


Every week you can add an hour to the photo period until you get to where you want it. It seems like a along time but if you dont many will bleach and possibly die. Its basically light shock.


I can count on 2 hands the number of people Ive meet who have wiped out half of there livestock by switching lights, (or bulbs) because they did not let the corals adjust to the new lights.

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Right now I'm running the light for about 6 hours a day. I ran the lights for the 2 hours you suggested for a little over a week, but have increased it about 2 hours each week over the past three. The corals were about 5-6 inches away from the 110w PCs, so I thought putting them 2+ feet away from the 250w MH would compensate. Would my best option now be to cut the light period down again and more gradually increase it, or move the affected corals back under PCs for the time being? Some of the frags I've moved (xenia and yellow polyps) seem to love the extra light.

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I disagree with changing photoperiod..period!:P


Seriously, though: your corals need to adjust to light INTENSITY. Running the much more intense light, even for a shorter period of time, may still burn them until the get used to it. You're better off propping up your hood, or raising it and gradually lowering your lights closer to the tank over a period of time.


To put it simply:your going from office lighting, then lying in noontime sun will most likely cook you. Maybe to a lesser degree if for a shorter time, but will most likely burn you. Doing the same, but under a shade, or if you could feasibly get further away from the sun, will allow your skin to slowly tan and get used to the intensity.


Stupid analogy, but hopefully my point came across. If there is no way to raise the hood, then place your corals as low as possible, and then use the potperiod trick as a last resort.


The fact that some of your livestock is doing well is OK, and they will be healthier (INO) with slightly less light but a standard photoperiod

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Bruce Dunphy

GREAT suggestion about the hood propping. I was thinking about some kind of screen material that wouldn't damage the tank, because I am going to be stocking in about a month with similar concerns. I don't want to mess with the photoperiod.

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Also helps with gradual heat adjustment, and give you a chance to plan for it, should you realize that the heat will be too high when it's set down to the regular operating height.

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