MH lighting 2 bulbs or 1

[floridagator]

getting ready to order some MH retro kits -- Help me make a choice

1 400 watt in the middle
2 175 watt
2 250 watt

also under the canapy i'll have 260 watts PC of Actinic (or is that to much??)

I was leaning towards the single 400 since it would be a little cheaper and only one bulb to purchase in the future.. however it doesn't look like many do that so i'm guessing it's better to have the light more spread out with bulbs on either side of the tank than just one in the middle.. thanks.

 

[EdKruzel]

I will assume this is for the 90 gallon tank listed in your bio and that it does not have a center brace?

One 400watt bulb will do provided it is placed high enough above the water surface and you keep the highest light lovers towards the middle.
Everything depends on the types of coral you wish to keep and how you intend on aquascaping the tank.

If you intend to keep a natural reefscape and light lovers throughout, then I would recommend 2 - 250watt DE fixtures.

 

[WaterKeeper]

I like two lamps myself. MH lights are somewhat like spotlights and their greatest intensity is directly under the lamp. Using two tubes helps spread the light more evenly. See The Lighting Thread for an in depth discussion.

 

[BeanAnimal]

Placing the light "high" above the tank to increase the footprint will also spill a LOT of the light out of the tank. In addition the light becomes less intense as it moves away (the bulb is a point source and subject to the law of inverse squares). You are MUCH better off with (2) bulbs closer to the water. You can then reign in the footprint and maximize the efficiency of the reflectors.

 

[Dubbin1]

You will need two bulbs since one bulb will only cover a 2' area.

 

[bertoni]

I'd probably use two bulbs. What are the dimensions of this tank? Either 175 W or 250 W might work, depending on the animals you want to keep and the efficiency of the setup.

 

[GSMguy]

2x250

 

[floridagator]

Thank you for the responses. seems like everyone agrees that 2 bulbs would be the best way to go with most saying 2, 250 watts. No problem i can go that route.

however with that being 500 watts and then 260 of Actinic = 760 or 8.4 watts per gallon for my 90 gallon- is that to much?? just seem like a lot - fish place said 5 watts and you can grow anything?? do i not need the actinics?? Thanks again for the advice - I want to make the light order this weekend.

Ed. yes my 90 does have a center brace on top - also what does DE fixtures mean?

Waterkeeper -- I read your lighting thread several times over the last month - great info!

 

[supertech3]

I agree with Bertoni on the dimensions can save you from having to use the 250w that the 175w could work. IMO I would ditch the PC lighting idea and go with the t-5 HO's

 

[bertoni]

Watts per gallon doesn't mean much, so I wouldn't worry about that. Actinic supplementation is for looks, so you might not even want it, although most people do, I think.

 

[floridagator]

not sure on the dimensions - it's 4ft long.. 90 tall i believe is what they call it. I already have a 48 inch Current pc that i was going to use for the actinic.

i guess to sum it up i'm asking what would the ideal light hood for a 90 gallon be.. I would like the flexablity to do a mixed coral tank

 

[bertoni]

I would use two bulbs. Given that it's a tall, 250 W is probably your most flexible option as far as bulbs.