lighting question
 

i got a 120gal reef tank, the size is 48x24x24
i use one 400w mh and two 110w (total 220w) vho actinic
so far the result is very good
i want to know if i cut down the actinic to one 110w vho
is that enough
how to calculate how many watt of actinic a tank need
thanks

I have the same tank and I am running 4 x 110 wt vho actinics with 2 x 250 wt MH.

The balance seems good to me. Lots of colour in the corals. Any less actinic I think my tank would be too white.

If you say your happy with it why would you want to cut down the amount of actinic?

Although one bulb might be enough if you are running a fish only tank.

Or if you are using 14000k MH or 20000k MH.

Try it out and let us know.

But for as the correct amount of actinic light a tank needs I don't know that answer. I would think more is better in most cases. JMO.

hth

actinic is mostly for aesthetics, so if 1 vho of actinic looks good to you, then so be it. :D

if you want to get more blue from your halides, please be advised that 14000k-20000k bulbs have less useable output than 10000k bulbs..so it's best you get the blue from your VHOs...unless of course your corals don't need that extra bit of light.

Uhm... I'm not so sure about this... I have always understood that actinics provide the spectral range that zooxanthellae require for photosynthesis... I could be wrong... but everything I have read points to this.

A 10000K MH contains more of that wavelenght than VHO actinics could ever provide. there for use your MH for lighting requirments for the corals and then ballance the color with actinic VHO's or what ever.

to show what I am meening a VHO URI super actinic puts out about 80 to 100 units of PAR at 12", a 175 watt ushio 10000K MH puts out about 180 units of PAR and my SA 10000K bulbs on a HQI ballast are pushing about 800 units. the biggest problem with using VHO Actinics comes in the form of penatration, the drop off through water is much higher than MH lighting. for example my URI's only have about 25 units at the bottom of my tank (so 1/4 in twice the distance) where my MH are still over 450 on the bottom.

Steve