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Re: Your suggestions for lighting please [f/u]
>- what do you suppose is the optimum color temperature for my lighting? I
>understand that 5500k bulbs most closely match sunlight (at the surface
>anyway). Is it safe to assume that most tropical FW plants are shallow water
>species and that bulbs designed to meet the needs of reef aquarists, i.e.
>actinics, aren't applicable? Some suggested 6500k bulbs or a mix of 6500k
>and 5500k. What's the rationale there?
5500/5600 kelvin is the approximate color temperature of sunlight in most
places. As you get very far north/south the color temperature starts to go
up (get bluer). The trouble is that the 5500 kelvin lights make the water
look a bit yellowish for some people's tastes. Many use 6700 kelvin lights
simply because they like the look of their tank better under the bluer
light. Stay away from the bulbs for reef keepers -- they are the VERY high
color temperature bulbs in the 10,000 - 20,000 kelvin range. Those bulbs
look BLUE rather than WHITE. If you want to duplicate the color under 20+
feet of water they are a good choice :-) I use 6700 kelvin lights over my
own tanks, with some 5500 kelvin lights on a few little 2.5 gallon grow out
tanks.
>- somebody mentioned noise as an issue related to MH. Would that be the bulb
>or the ballast? Is that a wide-spread complaint?
The ballasts tend to hum. My 400w ballast is very, very quiet and I have to
strain to hear it, and my 175w ballasts are about the same (the fan on the
ballast box is louder than the ballasts). Some people have complained about
excessive noise from the core+coil ballasts and switched to electronic
ballasts to stop the hum. I suspect that the ballasts are noisier under
certain electrical conditions, perhaps circuits with very poor power factor
(which I know makes all transformer devices more noisy), or maybe just low
or high voltage. My line here is about 122v most of the time and my
ballasts are nearly silent.
If you go to an LFS that has a lot of reef stuff you should be able to ask
them to show you a tank with MH lighting on it. Listen to the ballast(s) --
if you think they are quiet then you should be OK.
>- with a DIY or retrofit kit I guess I'd be mounting the reflector directly
>to the underside of the top of the canopy, correct? This would place the
>bulbs several inches higher than if they were in a hood placed directly on
>the aquarium. An eyeball measurement says about 8 inches, actually. Will
>this appreciably impact the amount of light reaching the bottom of the tank
>and thereby require more wattage? If so, how much would you say?
You should leave a gap of 1/2" or so around the reflector to allow for air
movement and cooling. With good reflectors you shouldn't have much trouble
getting most of the light output of your hood into your tank. The angle the
light hits the water determines if the light will enter the water or not.
In my own tanks with hoods I find that if I put the light a little higher
than normal (by keeping the water level a bit low), I get better lighting
with less dark areas.
>- lastly, in the DIY or retrofit scenario, should I leave openings in the
>acrylic top uncovered? Are there issues with humidity or moisture affecting
>the bulbs or connections? Is there actually a risk of water splashed from
>the surface shattering an MH or CF bulb?
The openings need to be uncovered for ventilation. This is especially true
for MH lighting that gives off a lot of heat. If you have the option,
mounting the ballasts in an enclosure remote from the hood will remove one
source of heat from the hood and keep it a bit cooler.
Yes, water can affect the connections. I've never had a problem with
humidity, but splashes can cause trouble. Splashing water on a hot MH bulb
is a sure way to get a bunch of glass shards in your tank. MH bulbs run
about 500º F on the outer envelope by my measurement (this is a 400 watt
bulb), and that might just be my probe's upper limit. CF bulbs run cooler
and are less likely to shatter on contact with water, but you should still
provide some protection. If you use a sheet of plastic make sure it doesn't
get too hot and crack or melt.
For wiring use water-resistant cable. Type SJOW is a good choice, but be
sure it is
105º C cable if it is going to be used with MH lighting or right up to the
bases of CF lights. The normal hardware store stuff is only rated to 90º C.
Carol and Essex both make good 105º SJOW cable (Carol's is called Super
VU-tron III), but only in yellow. Coleman cable (what I use) makes type
SEOW (they call it "Seoprene") and it is available in black.
If you go the CF route, AH supply takes care of most everything for you if
you use one of their kits.
-Bill