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[APD] Re: Self-ballasted PC lights?

I was wondering if anyone had ever thought about using or tried using self-
ballasted PC fluorescent lights (they have the ballast built into them so you
can use a regular lamp socket). I was considering using a couple 85watt 6500K
self-ballasted PC bulbs over my 65 gallon tank (that I will soon be setting up
as a planted tank). They only cost between $25-$30 and save you the cost of
buying (and replacing)expensive ballasts. I can see two possible problems with
this setup...

This question comes up periodically on the list so there are a bunch of threads in the archives about it.
BTW, a typical ballast for regular linear PCF lights will last more than 5 years IMHO. I wouldn't worry too much about factoring in replacement cost of the ballasts in your pricing calculations since you will be able to amortize the cost of the ballast over many years, and they aren't very expensive to begin with unless you're getting them from an LFS.

1) They are twisted bulbs instead of straight so they do not cover as much
area (they act more like a spot light)

They are closer to point source lights, but suffer from high restrike due to the coiled tube. In a normal linear florescent light, light radiates outward roughly equally in all directions around the cylinder of the tube (must... resist... using vector terminology....:-). In a tightly coiled tube, a lot of the light is emitted on the "inside" of the coil which does little besides heating up other parts of the coil. This reduced "effective efficiency" will translate to less of the light output getting into your tank, so a 55 watt incandescent-replacement type fixture will *not* produce the same *effective* light over your tank as a 55 watt "normal" (linear) PCF lamp would.

2) You can't buy regular lamp sockets that are water tight like the aquarium
fluorescent endcaps.

This isn't really much cause for concern. I really think the watertight endcaps are mostly marketing hype and have little technical value. Most of them aren't even truly watertight (or stop being watertight after a few months or years of exposure to the high-temp and high-humidity environment above a tank). I use "regular" bases over all my tanks since they are much cheaper and are easier to replace when they fail from corrosion and the like. And if your hot bulb goes in the tank there is a good chance it will break from the temperature shock and then you'll have electrical contact with the water despite having the watertight endcaps. My advice: use a lens of some sort between the water and your bulbs and don't worry about the endcaps, but use a GFCI on the electrical circuit feeding your tank equipment and *test it monthly*. Also, the breaker-type (as in mount-in-the-electrical-panel type of breaker) GFCI's tend to be far more reliable and longer-lived, IMHO, and I've seen a *lot* of both types of them.

However, the way I look at it, people use MH lamps and (although much
brighter) they act like spot lights too. Using a good reflector might help
with this problem too.
MH doesn't suffer from the restrike problem since it is a "true" point source light (all the light comes from essentially one very small spot and radiates roughly equally in all directions). As a result of this, it is not difficult to design a good reflector to direct most of the light into the tank. With a coiled PCF lamp, it is impossible to realistically design a reflector capable of using the light emitted on the "inside" of the coil, which results in that light being wasted in restrike, which does little beyond heating up the florescent tube.

As far as I am concerned, using a regular lamp socket MIGHT accumulate a bit of rust on it, but they only cost a few dollars... if they accumulate rust I can just replace them when I replace the bulbs and still save money. Coralife has the same thing in a 10watt version in either

Use a commercial ceramic light socket (even Home Depot has them) with brass contacts if you can find them (many use aluminum for the screw contact and brass for only the pin in the base). You can clean corrosion off of a brass socket with a scouring pad or a dremel with a wire brush disc. You'll get *years* out of even a cheap socket though unless you have water making direct contact with it over a prolonged period of time (such as in the case of a light socket placed over an area of the tank with an air stone, which will create a "mist" in the air above the water surface in that area).

6500k or 50/50(10,000k/actinic) so obviously people have thought of doing this
for small tanks. I am interested to hear what other people think about this

The basic consensus is usually that it can be done, and that the cheap lights will work, but they're not as good as a "real" linear PCF is in terms of efficiency or light delivery to the tank water. If you're on a tight budget, the incandescent-replacement type fixtures are definitely worth a try, but if you're looking for the best performance or electrical and lighting efficiency from your system there are much better options on the market.

Since it sounds like you are planning to DIY your lighting, have a look at the linear PCF supplies available at http://www.ahsupply.com. Many on the list (including myself) have had very good luck with their equipment, and the prices are much better than the prebuilt assemblies the tank manufactures sell.


***************************** Waveform Technology UNIX Systems Administrator

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