240w or 400 w

[jumeda33]

Hi all,

I have a question about lighting and depth of tank.

I have the All Glass 150 which is 72 x 18 x 29 according to their specs. The 29 is from the bottom of the tank to the very top. If I measure from the top of the sand to the water line it is about 25". I have the Lumen Bright pendants, 3 of them that have the bulbs approx. 15" above the water line. So the sand to the bulb measurement would be about 40". I was told to do it this way so the water didn't get so hot and the fans could circulate below them. Anyway, with all these measurements, should I be using 250w or 400w bulbs. Right now I use 250w 12k Coralvue Reeflux bulbs (single ended).

I am afraid that 400w will burn whatever is high up in the tank yet on the other hand I am worried that 250w is not reaching the bottom at maximum potential.

Whant do you guys think?

Thanks,
David

 

[yote]

If it was me.I'd just lower those 250s down to about 6 to 8 inches above the water.
That'll leave plenty of room for air to circulate and get the light where its needed at the same time.

 

[ndepratt]

MH's really don't lose intensity until they hit water... so lowering the lights a few inches really isn't going to do anything.

For a tank over 24" I would really go with the 400w. That'll give you good growth throughout the tank, not just towards the top. I really think you're going to look a little dim at the very bottom.

If you plan to do any sort of LPS on the bottom, or especially a clam on the sandbed... then it's definitely going to need to be 400. just my .02

as for burning/bleaching, just acclimate your corals and you'll be fine. You really should be doing that with either wattage. I would suggest looking in the coralvue 400W dimmable ballast, it has a 30% dim, and will overdrive 10% if desired. That ballast would be GREAT with the reeflux bulbs (both from coralvue).

 

[bjohanson1234]

Sorry that this is off topic or thread hijacking

But I saw that there are many dimmable ballasts on your site even for the t5's which is what I have. Are they manually dimmed or are they dimmed by sending a signal to a terminal? Dont know how else to explain it but I have installed dimming flourecents in a school auditorium and the whole school lighting was computer controlled it was really interesting. They even had sensors that if there was a bunch of sun light coming in, the lights would dim. Sorry about the hijacking but back on topic.

From what I understand, the sunlight that these corals see day to day is way stronger than a 400w bulb. As was stated before, it is a matter of acclimating them.

Brian

 

[ndepratt]

they are manually dimmable.

and you are completely correct, the lights we use are like candles compared to the sun. HOWEVER these corals typically aren't as shallow as they are in our tanks... so it's kind of a trade off. I would be interested to see what the average PAR is on coral reefs where, for example, SPS grows and clams live.