How far from water surface for 400w lights on 180?

[nightOwl]

My tank is 180 gallons and I am facing a very frustrating issue with some of my corals. They seem to be loosing color i.e. getting drab looking but some appear to be bleaching as well. The drab color makes me think not enough light but the bleaching makes me think too much light. How close is too close for 3 X 400 watt Radiums on a tank that is 72" x 24" x 24"? I know some people have their bulbs fairly close to the water surface. If you have a similar set up please share how close your bulbs are from the water surface and how long your photo period is. .

I also run 4 x 72" VHO's on the tank. I have since cut them off as one set is old and I think it is contributing to nuisance algae in the tank. The MH were running for 8 hours and the VHO's were on for 10 hours.

Water test results
10/11 -Fish store

• Nitrate - 1
• Alk - 3.6
• Calcium- 500+
• Phosphate - .05
• Magnesium - 1500+

10/19 - At home

• Nitrate - 0
• Alk - 2.4
• Calcium- 560 (Hannah Test)
• Phosphate - 0
• Magnesium - 1350

Any help is greatly appreciated...

 

[polywise]

NightOwl,
I had good results with my 280 72x03x32
4 400w 12k's
4 vho atinics

bulbs were about 10" above the waterline

 

[MB-84]

I have a 180 with 2-400watt 20k coralvue's with coralvue adjustable ballast with 2-72" super actinic vho's. I keep them about 15-18" above the water line.

 

[MB-84]

my vho's turn on at 10am and off at 9:30pm and the halides turn on at 12pm and off turn 8pm

 

[cdamiano]

It depends on what type of fixture/reflectors you are using. A high quality reflector like the lumenarc or lumenbright will require you to have the bulb higher than a lower quality reflector.

 

[Reef Bass]

My 400w MHs are 8" off the water on my 24" deep 100g. I run them 8hrs a day, plus 2 T5 actinics which are on for 9hrs a day.

What you really want is to measure the par in your tank. That is far more accurate a guage of light level than how high one's lights are.

 

[Pallobi]

What you really want is to measure the par in your tank. That is far more accurate a guage of light level than how high one's lights are.

agreed...

 

[nightOwl]

Thanks everyone so far! I forgot to mention the type of reflectors. I think they are Lumenarc reflectors. I am in the process of trying to get the PAR meter from my local club but the two we have have waiting lists . I have a Lux Meter which I know is not the same but it may help me shed light on how much light is reaching the bottom my tank. I guess I will have to start digging to see what kind of numbers I should see. I recently came from the T5's on a 90 and I was getting great color. Now on my bigger tank I have seen corals fade and it bothers me.

MB-84 - How far off the water surface are your bulbs?

 

[Reefsi]

Correct me if I am wrong but the bleaching is more than likely caused by the off balance of alk/calc. The calc being 500+ and alk 2.4 is out of the levels for maintaining sps. I would work more on balancing these levels. Just my 2 sense.

 

[Reef Bass]

Reefsi, I'm betting his alk is 2.4meq/l, not 2.4dkh, though it's hard to be sure without the OP explicitly stating.

 

[nightOwl]

Reefsi, I'm betting his alk is 2.4meq/l, not 2.4dkh, though it's hard to be sure without the OP explicitly stating.

Reef Bass - What you stated is correct . The alk is 2.4 meq/l and 6.7dkh which I think is within range. A bit on the low side but alk overdoses are the worse so I prefer to have some wiggle room.

 

[chuckreef]

Some of the corals???

Please provide more info

Could be low light corals in the wrong place, but, er, it could also be other things?
Is some of the corals all acros? Or , all montis?

 

[flyin2jz]

How is your coralline algae growth? I have 3 250w radiums over my 200 that are about 10in from the water surface and i cant grow a single spec hardly of it. I went and put eggcrate and screen over it and it grew like crazy and the alk and calc were all in check. I just put some 14k plusrites on the tank to see how they look as the radiums needed replaced. Its a ton brighter so im thinking the screen may have to come back out. Ive seen tons of tank with good algae growth including tanks ive owned just not this one for some reason.

 

[nightOwl]

Some of the corals???

Please provide more info

Could be low light corals in the wrong place, but, er, it could also be other things?
Is some of the corals all acros? Or , all montis?

chuckreef,
It is a combination of acros and monti's I don't really have any low light loving corals in my setup. I think it is more of converting over from T5's that were in some cases 5 inches or so from some corals to MH. Now being a lot further from the corals in the tank.

How is your coralline algae growth? I have 3 250w radiums over my 200 that are about 10in from the water surface and i cant grow a single spec hardly of it. I went and put eggcrate and screen over it and it grew like crazy and the alk and calc were all in check. I just put some 14k plusrites on the tank to see how they look as the radiums needed replaced. Its a ton brighter so im thinking the screen may have to come back out. Ive seen tons of tank with good algae growth including tanks ive owned just not this one for some reason.

flyin2jz,
In my old tank everything was covered. I checked today and I have some spots on the overflows and on the back wall but now as much as I expect I should have. I am starting to feel like you on the tons in the past and none on this one. It is very frustrating!


I am in the process of trying to borrow the PAR meter for our club but the line is so long.