Lately on the forums I’ve been seeing a lot of talk about what is the best lighting to buy. Now I am not going to discuss which is the best brand, bulb or the like. I am going to give you a run down on lighting. It seems more and more people are confused with all the different types of lighting on the market today, with various ratings, wattages and prices it can become very confusing very fast.
Wattage per Gallon rule.
Have you heard of the wattage per gallon rule? I am sure many of us have, it states: “reef system calls for 3 to 5 watts per actual gallonage of water.” To illustrate why this rule is invalid, look at the below illustration. Do you notice anything about it?
Those are 2 55 gallon tanks, the only difference is the one on the right is taller than the one on the left and therefore the wattage rule would not be valid. It does not take into account the height of your aquarium. Whoever came up with this “rule” needs to be taken outside and shot. This alone gives most reef beginners incorrect information when they are shopping for their next lighting system. This wattage per gallon rule is okay I suppose if you want to keep a fish only tank, please do not follow it if you plan on keeping a reef tank.
What are Lumens?
Lumens is another area of common confusion. Wattage is the “power” of the tube. Lumens are the actual amount of light being “radiated”, or the amount of light energy reaching the animals created by the power output of the tube. That wasn’t confusing now was it?
Basically, and without getting into a deep science seminar, the lower the Kelvin, the more yellow the light. Hence, the higher the Kelvin, our light appears starkly white or blue-white. Getting way up there into the 20,000K range, the bulbs actually appear to glow dark blue! Lighting with 10k bulbs will allow your corals to grow faster then lighting with 20k bulbs. However, most corals look better under 20k bulb lighting. Which is more important to you? Having your corals grow faster, or making them look prettier. It is entirely up to you!
Reef Tanks with T5 or Metal Halide?
If you want to start a full reef tank, you need at least T5 lighting or Metal Halides, although I have seen some tanks with PC (Power Compact) lighting. If you want to keep a fish only tank, or a fish only with live rock (FOWLR) your not going to have to worry about buying intense lighting. You won’t have to worry about it unless you plan on keeping SPS (Short/Small Polyped Stony) corals. The only difference between a T5 unit and Metal Halide besides the wattages is the shimmering effect on your live sand and your aquarium that you receive when you choose Metal Halides. SPS will love T5 lighting as much as Metal Halide’s. This choice is entirely up to you.
Why do SPS corals needs strong lighting?
SPS (Short/Small Polyped Stony) use photosynthesis to survive. Just as plants convert sunlight to produce chlorophyll, marine animals survive similarly by converting light energy into “food”. Actually, this energy is consumed by zooxanthellae algaes that produce by products that the corals need to survive; a true symbiotic relationship. Without strong lighting, the zooxanthellae algaes would die, and the coral would slowly starve to death, the coral then turning white.