I think there are to many variables to just say one,s a 400 and the other,s a 250, so its fine. The 14k 400,s are not the brightest, although a nice bulb. If they were something like Ushio 10K,s then I would say no problem.
You also had then a decent height, as are the 250,s but covering a 5 ft. by 27in. span.
The new bulbs are HQI, which I have never used, but always thought were at least the equivilent par of higher K 400,s. Second, they are only covering a 3ft. by 18in. space, a lot less, meaning your corals are getting a lot more light.
Also, your sps have been in minimum light for several day,s so that should be taken into account.
Its possible with the height your running the 250,s that you may be fine, however I would still error on the safe side. Having never used the screen thingy though, I cant say how much or for how long. Would not think as much as getting new, low K bulbs or going up in wattage. Like I mentioned, perhaps the height alone is enough, but Ben swears by the screen method.
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Doug
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