Going VHO vs MH

[Bearfan]

I'm researching new lighting for my 75gal and was wondering the advantages between [acronym:b4d6838775="Very high output fluorescent"]VHO[/acronym:b4d6838775] and [acronym:b4d6838775="Metal halide light"]MH[/acronym:b4d6838775]. From what I read, [acronym:b4d6838775="Very high output fluorescent"]VHO[/acronym:b4d6838775] runs cooler.

I debating between 7x110 [acronym:b4d6838775="Very high output fluorescent"]VHO[/acronym:b4d6838775] (5 daylight, 2 actinic) or 2x250 [acronym:b4d6838775="Metal halide light"]MH[/acronym:b4d6838775] + 2x110 [acronym:b4d6838775="Very high output fluorescent"]VHO[/acronym:b4d6838775] actinic.

Anyone want to suggest?

[PC]

I run 4 [acronym:aa8ce8ebd7="Very high output fluorescent"]VHO[/acronym:aa8ce8ebd7]'s (2 actinic blues, 2 actinic whites) over my 75G and everything is good..[acronym:aa8ce8ebd7="Metal halide light"]MH[/acronym:aa8ce8ebd7] would roast my tank in the summer considering I would need at least a pair of 250w 12k or 14k mh to do the same work. Heat will most definitely be your enemy with [acronym:aa8ce8ebd7="Metal halide light"]MH[/acronym:aa8ce8ebd7].

[Salttanker]

Heat is definitely an issue with [acronym:5c2b99b912="Metal halide light"]MH[/acronym:5c2b99b912], but if you build the canopy high enough and add a couple of fans it will only change within a degree or two. I love mine. The shimmering effect is pretty awesome too. I have the 14K Coralvue's and can run them without supplemental lighting. It offers a nice white, and blue balance. In fact, I just use my actinics without the whites on my [acronym:5c2b99b912="Power compact fluorescent"]pc[/acronym:5c2b99b912] for the dusk to dawn effect.

Mike

[msuburg]

I'm currenly setting up my 75g, and I think I'm going to go with the VHOs myself. The [acronym:e2252f0bcc="Metal halide light"]MH[/acronym:e2252f0bcc] scares me a bit with the heat. And I don't think my canopy is going to end up being that high off the water for the [acronym:e2252f0bcc="Metal halide light"]MH[/acronym:e2252f0bcc].
With the VHOs, should I just go with 4 of them, 2 actinic white and 2 blue? What differences would it make to do different numbers of these - say 3 white and 1 blue? Is it just shifted towards one end of the spectrum? Or should they always be equal, such as 2 x 2?

[acronym:e2252f0bcc="Thanks in Advance"]TIA[/acronym:e2252f0bcc]

[Phyl]

Will you get the same light penetration with VHOs that you would get with [acronym:aa2c3a5773="Metal halide light"]MH[/acronym:aa2c3a5773]? This whole lighting calculation has be a bit confused. It seems like light penetration would be more important than [acronym:aa2c3a5773="Watts Per Gallon"]WPG[/acronym:aa2c3a5773]. Sure I could put a second light just like my first over my tank but the bottom would still be getting the same intensity of light (just more of it)... What is the penetration difference between [acronym:aa2c3a5773="Very high output fluorescent"]VHO[/acronym:aa2c3a5773] & [acronym:aa2c3a5773="Metal halide light"]MH[/acronym:aa2c3a5773]? Is it comperable? Could I double my [acronym:aa2c3a5773="Power compact fluorescent"]PC[/acronym:aa2c3a5773] and get to the same place?

[bound_for_obx]

Couldn't you get by with 2x175 [acronym:ccdcf935c6="Metal halide light"]MH[/acronym:ccdcf935c6] and 2x110 [acronym:ccdcf935c6="Very high output fluorescent"]VHO[/acronym:ccdcf935c6] actinic? You are only talking about penetrating about 16 inches of water with a 4" [acronym:ccdcf935c6="Deep Sand Bed"]DSB[/acronym:ccdcf935c6] in a 75 [acronym:ccdcf935c6="Gallon"]gal[/acronym:ccdcf935c6] tank. You would have less heat to worry about and I would think that that would be plenty of light. It would cost a little less to set-up, operate, and replace bulbs as well.

[PC]

I have a 150w [acronym:4493d1ea3d="Metal halide light"]MH[/acronym:4493d1ea3d] w/2 65w blues over a 29G and it can take the temp 2 degrees up over 5 hours. It very much depends on what the temp is in the room. This tank is upstairs and the temp (room t emp) can be controlled much better up there than in my downstairs. I imagine during the summer its going to be very hard to keep the temp in the mh tank stable as it will get very hot where I live in the summer (Can get into the 100's easy). My point being, that if you live in an area where you can expect very hot temps outside, you can expect its going to get pretty warm inside. If the temp in your house is 78, the tanks going to be *at least* that much which means another 5 - 8 hours of mh lights (even dual 175's) are going to cost you another couple degrees (Min). So at the end of a 5 hour cycle your tank temp would be about 80.? degrees. Now, barring the fact you may have a pile of money or an industrial [acronym:4493d1ea3d="Activated Carbon"]AC[/acronym:4493d1ea3d] unit on your house, you'll probably end up with a chiller, running your [acronym:4493d1ea3d="Activated Carbon"]AC[/acronym:4493d1ea3d] all the time every day through out summer or dealing with high tank temps (usually treated by moving the cycle to cooler evening hours and using a fan (like a room fan) to blow across the lights to try and exhaust some of the excess heat..Great for the fish, not so much fun for the rest of the family..). All that said, even using 4 [acronym:4493d1ea3d="Very high output fluorescent"]VHO[/acronym:4493d1ea3d]'s I get a degree or two of flux and during the summer my tank can easily start to reach 82.? degrees. Its a given that mh produces more heat and that can only mean higher temps. You can put what ever wattage bulb you want over the tank, the fact is mh *is* hotter and will cause substantially more temp issues during warmer weather. Again, I have seen chillers used, I have seen folks run their thermostat (in the house) around 74 - 72, but [acronym:4493d1ea3d="in my opinion"]imo[/acronym:4493d1ea3d], thats not practical. I can't afford a $250/month cooling bill ; ) So in the end, you either realize mh may cost you a $400 - $800 chiller (plus the cost of running that each month) or run cooler lighting/change the light cycle to cooler hours..Not much fun to look at the fishies in the dark when you get home from work..
Just punchin' in with my experience, some of you surely live in cooler climates and may not have this issue.

GL!

[PC]

Sorry was goign to post this too, hit submit instead..
Taken from http://www.marinebiology.org/coralbleaching.htm ...
"
Temperature

Coral species live within a relatively narrow temperature margin, and anomalously low and high sea temperatures can induce coral bleaching. Bleaching events occur during sudden temperature drops accompanying intense upwelling episodes, (-3 degrees C to –5 degrees C for 5-10 days), seasonal cold-air outbreaks. Bleaching is much more frequently reported from elevated se water temperature. A small positive anomaly of 1-2 degrees C for 5-10 weeks during the summer season will usually induce bleaching. "

Alot of issues are temp related most folks don'realize it. Not trying to say mh is evil (I have mh!) but be prepared to deal with the heat issue. Know your coral, in some instances it only takes a degree or so to cause the symbiotic zooxantheallae to start to die off..

GL!

[scuba_steve]

bearfan with your huge sump in the basement you wont have an issue with heat ! id go with 250watt hqi 20000k and no need for o3 supplement

[Salttanker]

One thing to keep in mind is replacing bulbs every 6 months or so with [acronym:d96833d198="Very high output fluorescent"]VHO[/acronym:d96833d198]. If you have 7, that will get pretty expensive. [acronym:d96833d198="Metal halide light"]MH[/acronym:d96833d198] bulbs are more expensive (mine are $56.00 each), but replacement is within a year, and that would only be 2 of them versus 7 every 6 months. I like Keith's idea with going for the [acronym:d96833d198="Metal halide light"]MH[/acronym:d96833d198] with the 20K. 2 of those, and no additional supplementation would be ideal for a 75. Food for thought..

Mike