The hybrid solution with LEDs to get the optimal reef system in terms of resembling natural environment results is mostly to get those LED lovers to enjoy the LED visual effects that halides and/or T5s will never be able to IMHO. Many friends are already doing that, leaving their LEDs on when they come back from work at night, and halide/T5s during the day for the "punch". I personally don't care for the LED effects and therefore sold my fixtures long ago. It is a solution for visual appealing but unnecessary in terms of saving electricity or to achieve the optimal results. All my systems with LEDs, T5s and/or with halides had basically the same amount of electricity usage because the photoperiod had to be adjusted in order to avoid photoinhibition in each case. Chiller would have work basically the same in every situation because of that also, so it wouldn't matter much money wise. Initial cost with the LEDs in the combo will be unnecessarily higher in my point of view. I do not condemn such combos though. This is just a hobby and should be enjoyed as each of us wish, personally. Combos like that will bring much better colony structure, color and healthy growth to any system. It is also important to note that halides alone will supply most, if not all, the needs one would have to offer in order to achieve those optimal results. Best combo that I use and recommend is metal halide/T5 system.
I agree MH/T5 combo is more than good enough to provide all the spectrum need for coral. In the old time before T5 came along, all we got was MH starting with 3000K then another kind of metal halide lamp is the halogen metal iodide or HMI lamp. It is mainly used for photography since it makes a 5600K light (matching natural daylight) and has a great CRI. The lamp has a optimum combination of metal halides made of rare earth metals. It has a quartz discharge tube with rod-shaped electrodes made of tungsten and a power supply of high voltage DC .
As each year go by MH keep improve to specific commercial need and finally translate to aquaculture and horticulture that produce more blueish spectrum that raise the color temp to 20K and beyond, I find an european company actually produce 30K MH that can help to boost that coral fluorescent but not nearly enough like led blue spectrum to create that artificial pop that why led being incorporate to produce the candy effect to the eyes which my visit friends and family members prefer the look.
I am ok with either look but much prefer the natural look as the coral would be in the nature as I know it's not really that beneficial to coral long term health when certain UV and blue spectra would cause such reaction.
Corals generally get their glow from fluorescent pigments that act as sunblock. The sun's intense rays, which can sunburn swimmers and divers that flock to these reefs, cause similar damage to coral and zooxanthellae, the symbiotic
algae that lives inside coral.
When scientist illuminated the corals with blue or ultraviolet light—mimicking what's found in the ocean depths—he found that they could also glow red or green. Interestingly, he also discovered that the corals could produce these pigments in the absence of any light at all.
This, combined with the general lack of sunlight at these depths, means that these pigments weren't acting as a sunscreen.
Instead, the researchers believe that the pigments help make more light for their symbiotic algae, which need it for photosynthesis. Happy algae translates to more oxygen and other benefits for the coral.
In essence, blue spectrum produced by led has certain advantage to a reef tank but to growth solely on leds is not efficiency IMHO.
When I mention the term intelligent schedule meaning, when I run my reef tank in winter as Canada is very cold during winter month, I will increase my MH time upto 8 and even 10 hrs as it provide heat to my tank so that I don't need to depend much my heater to keep my tank warm that much.
In summer I may only run 4 hrs or less depend how hot it is and I don't use chiller to cool it down by intelligently boost more time to led running while reduce the MH and T5 down, I don't use chiller to cool it down but rather using fans to blow at tank surface that keep its cool enough but I keep refilling the RODI water to compensate the water evaporate.
So in essence I still say the initial cost of led is higher.
