Transition from MH / VHO to LED - Input Needed

[SharkB@it]

I posted a thread last night, but it doesn't look like it published so we'll try this again.

120g (48x24x24) mixed reef tank currently lit by 2x 250w MH and 2x VHO. Time to replace bulbs and looking to transition from MH/VHO to LED. Purchased a Kessil AP700 which, based on mfg specs, seemed like the correct size for the 48x24 footprint assuming I can mount high enough in the canopy.

Questions:
1) My original intention was to fully replace the MH/VHOs, but I'm reading where people are using a combination of lighting to supplement the LEDs. Is this necessary and advisable? Assuming yes, how does one determine the ideal mix?

2) I've read about the acclimation period adjusting the corals the the stronger LED light to prevent burn / bleach. If I'm starting at low intensity to prevent scorching the corals near the surface, are there concerns of the corals closer to the sand bed not getting enough light? How do you address?

3) what considerations am I blindly overlooking? Anyone who has made the same transition have an advice or input?

Thanks in advance!

 

[alton]

Beg, borrow or steal a PAR meter and try to match your MH by 75%. Watch the BRS video and you will notice they have two on a 120 gallon tank. 185 watts of led is not going to replace 500 watts of MH. I am sure you will get plenty of responses in the near future. Kessil leds grow corals, but they seem to create a bunch of shadowing from their led fixtures following their recommendations.
Welcome to Reef Central

 

[Tripod1404]

1) My original intention was to fully replace the MH/VHOs, but I'm reading where people are using a combination of lighting to supplement the LEDs. Is this necessary and advisable? Assuming yes, how does one determine the ideal mix?

Necessarry? No. Advisable? Yes, because it greatly reduced the self showing issue and spectral coverage limitations of LEDs. Most high quality LEDs can already give good amount of light in blue spectrum, for supplementary bulbs (which are mainly T5HOs), I would use something with very wide spectrum (like ATI coral Plus). Most people use 2 to 4 bulbs, depending on depth and how much light they need.

2) I've read about the acclimation period adjusting the corals the the stronger LED light to prevent burn / bleach. If I'm starting at low intensity to prevent scorching the corals near the surface, are there concerns of the corals closer to the sand bed not getting enough light? How do you address?

It should be gradual, corals at your sand bed are also acclimated to lower light compared to ones on the top. So light being lower on the bottom would be ideal, not to bleach those guys. If you have a par meter, measure what you have now and adjust the LEDs to provide 70-80% of that (if no PAR meter, start the LEDs at 25-30%) . You might also shorten the photo period for few weeks. After that if corals dont look like bleaching, you can increase intensity 5% a week until you reach your desired intensity. Stop or slowdown if you see and sign of bleaching, being a good observer is the key (more so if you dont use a PAR meter).

3) what considerations am I blindly overlooking? Anyone who has made the same transition have an advice or input?

Try to keep the LED fixture as high as possible. LEDs can produce hot spots, being higher spreads these hotpots. It also reduces the self-shadowing issues. You would probably not need to run your LEDs at 100%, so keeping them higher and increasing the intensity is better than keeping them lower and running at a lower intensity.

Also, I would try to keep white channels low and use full spectrum-like supplemental T5 bulbs. Some coral have hard time adjusting to high intensities of white LEDs.

 

[dz6t]

I am always wondering how good VHO is provided you stock up replacement bulbs.



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[lancesmith1]

VHO is great but not as efficient as T5 if you are looking at fluorescent lighting.

 

[alton]

T5 is only as good as the the clean reflector used. I have seen aquariums where the reflectors where no longer reflective. VHO on the other hand had internal reflectors and Actinic is still unmatched. Sorry about getting off topic