metal halide lighting

[GREATMIKE]

I am running two 250 watt metal halide lights on my 150 gallon high.my coral seem to be growing very slow.am i better off changing my lights to 400 watt metal halides.and will this change,increase the heat load on my tank.or am i better off adding an other 250 watt metal halide light.bulbs are 14k

 

[fritz]

There's more to this than just the lights. Wait, why am I typing in bold...much better .What type of corals are you referring to?

 

[NYCrab]

GM -- It really depends on the dimensions of your tank - primarily its depth. Assuming it is a typical 6' x 2' x 2' layout, 250w is certainly enough to penetrate that depth, and you'd be better off adding a third fixture - as it is often suggested that MH bulbs be placed at 2' intervals. If your tank is shorter and deeper, going to a higher wattage may be the way to go. Although, in both scenarios, it depends on what type of bulbs you are using, how large the reflectors are, etc. Sanjay Joshi from Penn State has put out a lot of research on MH bulbs, ballasts and reflectors that can help put things in perspective. Hope this helps.

 

[scumonkey]

14k is probably your problem....
it (i've been told), has the lowest par of the 3 choices.
10k corals grow fast but don't look as colourful
20k corals look best but tank can look blue
14k looks nice but with low par-corals grow slow
My tank is 30" deep, I use 250 w 10k XM's, my corals grow like weeds!

If my info is wrong somebody else please correct me.

 

[reefman]

i thought 20k puts out the least par

i'm thinkin as a general rule
6500k puts out the most
then as u go higher the k, the less par

 

[fritz]

20k is the lowest
The closer to 6,500k the higher the par. The closer to 50,000k the lower the par. I wouldn't say 14k is your problem. Plenty of people get great growth and color with 14k bulbs. Light just provides a means of food for the coral. This food can be provided without the light and you can still get growth. I had a thread up recently where I got surprising growth in my acros with only 108 watts of T5!! There are others on here as well.

As was stated if you have a 6 foot tank you're going to want to have 3 MH bulbs, one every 2 feet. If your tank is deeper than 24" you might want to consider going to 400watt bulbs as they will penetrate deeper.

There's a quote with corals, that they need:
flow, food and light and in that order.
Make sure to check calcium & alk levels as those play an important role in growth. They're quite literally the building blocks of stony corals. Assuming that their needs are being met look for things that could stunt their growth. IE if the coral is spending energy fighting with another coral that takes away from the available energy that could be used for growth. You don't want to crowd corals or place them near "aggressive" corals.

 

[scumonkey]

i thought 20k puts out the least par

so did I... until I read an article that showed otherwise!
But you can't always believe everything you read so....
if anyone has hard facts please enlighten us!

 

[fritz]

http://www.reeflightinginfo.arvixe.com/
Go nuts, all you ever wanted to know and then some about bulbs and ballasts.
It's a general rule as the 175watt 15k iwasakis put out the par of a 10k 250watt bulb. Plus some bulbs and ballasts don't put out much par at all, cause they suck. In general maker X's 10k bulb will have more par than their higher k bulbs. PAR is a measure of light within the spectrum usable for photosynthesis (it's not blue) so the more blue, the less photosynthesis.

Par is not the be all end all of coral growth. Plenty of people get great growth with (relatively and comparatively) low par bulbs like Reeflux. Some people on this board have noticed the same growth going from 250s to 175s. It's a good guide but not the "secret ingredient" A good reef is the sum of all parts.

 

[GREATMIKE]

my tank is 4 ft x 2 ft & 32 inched deep.what would be the better way to go .I am going to go back to 10k bulbs for sure.shoul i add a third metal halide or just change both my light to 400watt.all my water level are normal.

 

[scumonkey]

you still haven't mentioned which corals your trying to get to grow?

 

[fritz]

I'd go with 400 watts for that depth and no you only need two. One MH bulb covers a 2 foot by 2 foot area. If it's a softy or LPS tank you could get away with 250s but for sps I'd do 400s.

 

[fali]

first research what kind of corals you have and if they need that much intense lighting. I don't see a need for 400 watt bulbs unless ALL the corals you have demand it. That will drive up your electric bill because of the higher wattage and the fact your chiller will be working overtime to cool your tank from the extra heat being generated. My tank is 29 inches deep and i have 150 watt MH 10k and my corals are doing great. However i will upgrade to 175 watt 10k maybe 250. This is just my opinion. Keep in mind not all corals like intense lighting, in fact i heard blastomussas will bleach under intense lighting. When corals are fully acclimated to your tank, happy, being fed, getting acceptable flow and lighting they will grow faster. Some coral species grow faster than others.

Please correct me if i'm wrong.

 

[fritz]

No, you're spot on.
LPS & softies don't need bright light
SPS don't need it either but it really really helps.

A good point that I forgot to mention is Single Ended vs. Double Ended bulbs. They are NOT the same. If you're using DE (Double Ended) 250 watt bulbs you'll find they are pulling almost 400 watts through them. 150 watt DE bulbs for example use as much electricity as 250watt MHs (which is why they are just as bright). Magnetic ballasts, in general push far more electricity through the bulb than an electronic ballast will.

 

[GREATMIKE]

sps corals

 

[cali_reef]

If you're using DE (Double Ended) 250 watt bulbs you'll find they are pulling almost 400 watts through them.

Not true at all, which bulb and ballast combo pulls 400W and what is its PPFD?. It is the M80\HQI type ballast that pulls more power than the bulb is rated for, an Icecap will use about the same power to drive both DE and SE bulb from the same manufacture.Try to pull the info for 250W XM bulbs since Sanjay have tested both types. M80 ballast are not as efficient in driving any bulbs as Icecap electronic ballast, most of the efficiency lost can be felt as heat on the ballast.

150 watt DE bulbs for example use as much electricity as 250watt MHs (which is why they are just as bright).

Which 150W bulb are you referring to? I have tried just about every type of 150W DE bulbs and I have not come across one using more than 200W of power on a PFO M81 ballast. They are far being as bright as a typical 250W bulb.

 

[cali_reef]

my coral seem to be growing very slow.

What makes you think your coral is growing slow and why do you think the light is the cause?