Metal Hailde distance from the aquarium

[kdejour]

My question here is. I have a 75 gallon reef tank. I have a spaghetti finger, quite a few mushrooms, starburst polyps, and a crocea clam. Water quality is excellent thanks to the help I received on nitrate reduction from you guys. I have two 250 watt mogul based 10k mh and two 110 actinic vho's. I have it suspended about 18 inches from the aquarium is this too high? I have a typical sized aquarium 4 feet long etc. Please advise. Thanks 8)

 

[SnowManSnow]

There isn't a set formula for MH height above the tank. You just have to experiment over the next week or so as to how close to the water you can get it without spiking the temp. I assume you're talking about a pendant? I just did the same thing on a 40g tank with 250w. I think I ended up about 11 inches up.

If it is a new MH light setup you also want to be careful to acclimate your tank to the new intensity. You may want to start it 24 inches or so (maybe even higher) and move it down 3 or 4 inches a day untill you reach where you want it. Particularly with your clam.. if he isn't use to the intensity Id be careful.. you can also just cover his part or corner of the tank with somthing to help.

Good luck!

B.

 

[Len]

It's really a reflector-dependant variable, but most are designed to work best 10-12" above the tank. The higher you suspend it, the wider it will distribute the light. The downside is any given area will receive proportionally less light.

Are you using a reflector? It's really a must; a good reflector can effectively double intensity.

 

[kdejour]

It came with a german polished reflector. I puchased this system from pet supply liquidators. I was made buy catalina aquarium.

 

[NAYM]

Mine is set at 11" above water level.

:lol:

 

[danmhippo]

There is no set rule, but you want to make sure the bulb got enough clearance from occasional water splashes, either from surface agitation, or fish jumping.

Otherwise you need some sort of shield (glass) between the bulb and the surface.

 

[Anonymous]

Ditto to what damnhippo said. NayM Aren't you worried about a possible splash up? My clowns splash up to my canopy all the time. Thank God I have a shield. Plus I am a klutz.

 

[danmhippo]

My pendant has a glass shield and is hung 18" from the surface. However I still find splash marks on the pendant glass shield. Sure glad that I have the glass shield.

 

[Anonymous]

Inverse square law = light intensity decreases with the square of the distance above the surface.

so, if the bulb is 8" above the surface 1/64th of the intensity at the filament is striking the surface at an average point within the beam. move it to 10" and it's 1/100th. 18" seems to be WAY up there.

So if only 1/64th is making to the surface for an 8" bulb height, guess how much makes it to the tissue of the corals.

FWIW I'd go with 8-10 inches max. I've never had a bulb pop from water slpash.