..D.E. wrote:
: Last year my fixtures packed it in. I looked at using T5 bulbs, but the
: ballast wouldn't support them. I then looked at replacing the ballasts. A
: new fixture was $2 more expensive than the ballasts and the fixture had a 1
: year warranty. So, now that T12 tubes are getting harder to find, I may just
: have to switch to T8 bulbs.

There are a few incompatabilities with T5 tubes, so it's frequently cheaper
to just get a new fixture.

(1) the end cap pins are narrower than the ones we are familar with on T12,
T10 and T8.

(2) T5 lengths are metric and don't match up well with the common 48 inch and
24 inch lengths we see on commonly available T12, T8.

(3) The T5 ballast drive currents are a bit different while the T12, T10,
T8 were designed to be backwards compatable, except for really lame ballasts.


: I was running a 50 watt CF on my older 27 gal hex, but have since gotten rid
: of that tank. I did like the lighting of the CF's, but the bulbs now are
: expensive. The T5's look promising, but will they still produce the wattage
: I need? I need at least 2.42 watts per gallons to maintain my tank. I would
: like to increase the wattage to 3 watts per gallon.

Light is not measured in watts per gallon.

T5s (not the HO style) generate more light per watt than other fluorescent tube
types. The older T12 tubes deliver less light per watt than other tube types.
There is something of a 40 percent difference in emitted light per watt when
comparing older T12s to newer T8s and T5s. Reflectors or lack-there-of
introduces another 50 percent or more difference on how much emitted light is
actually sent down into the tank. This should prove beyond a doubt that watts
per gallon is a very rough estimate.

I tend to think in terms of normally driven linear tubes accross the top of a
tank when there is a decent curved reflector for each individual tube.

One tube is low light
Two tubes is medium light
Three tubes is high light
More than three tubes is very high light

For the above options at T12, T8 and T5 the amount of light is roughly the same,
but watts per gallon number will be different.

This doesn't take into account the depth of the aquarium, but it seems more
useful than the watts/gallon which makes PC fixtures appear much better than
they really are.

PC and T5 HO are driven with more electricity, super charged in a way, so they
are bit less efficient. T5 HO is about the same as the efficiency of T8, most
PC are a worse than T8. PC has bent-back tubes which wreck reflector efficiency,
so alot of light for PC does not make it into the aquarium.

At this time, there are two obvious choices for long tanks:

T8. If you are a tinkerer, this is a great choice. Lots of people have been
modifying their T8 fictures and sharing tips online. These guys know how to
get the best results for their money.

T5 HO. Consider a TekLight I have a 6 tube T5 HO light where I only run 4 of
the tubes for only 6 hours a day. More than enough light. Solid all metal
fixture with enclosed electronic ballasts that does not need a fan. Other
vendors do have T5 HO lights, some are not so good. Compare against the TekLight.

Have fun with your lighting upgrade!