my lights?

[dochollow]

morning fish people,
i have 2 tanks, some of the bulbs are several years old, would like to upgrade/improve bulbs? the more i research/read the more confused i have become
on my 55 i have, 2 GE plant & aquarium bulbs
f40 wide spectrum in a shoplight
fixture
1 all glass aquarium bulb 32 watt
h.g. in a 55 gal strip fixture.
all 3 are 4 ft.
d.i.y. hood coming soon.
does this mean i have 2 watts per gal?
on my 29 i have, 2 ECOLUX plant & aquarium bulbs
f-20 20 watt wide wide spectrum
in a shoplight style fixture
1 lights of america F17 t8, 7800k
supposed to be 75 watts according
the package?
in a d.i.y. hood. all 3 are 2 ft.
does this mean i have 4 watts per gal?
any suggestions as far as new bulbs go would be greatly appreciated.
thanks, DOC.

[Trillianne]

My understanding is that Watts per Gallon is a rather older method of figuring out how much light you need for your tank. It hails from the era of not having a wide variety of bulb and reflector types.

To calculate it you add the watts of your bulbs and divide by the gallons in your tank.

The best illustration of the differences that have happened is this line:

1 lights of america F17 t8, 7800k
supposed to be 75 watts according
the package?

Based on my reading what you have is a 17 watt bulb, that has the equivalent output of a 75 watt bulb.

What has happened in the intervening years is that we have improved our ability to get more light using less energy. You get more effective light out of less wattage. We have also learned about distance from source to substrate matters, as well as nutrient availability matters.

So... one method that is fairly reliable is you can get a PAR meter. This measures the effective light getting from the light source to the placement of your plants. OR... you can wing it and guess and tweak until you get what works for you.

[Sandz]

Good info. Another tidbit on lighting is that you want to look at the color temperature of your bulbs. 6500k is the best for plants and best resembles the natural sun. 10000k is used for salt water but will be an algae magnet. No matter the fixture you choose to use, try to stay with 6500k bulbs. I find this more important than W/G.

[dbosman]

morning fish people,
i have 2 tanks, some of the bulbs are several years old,

Ignoring the rest, new bulbs/lamps/tubes will dramatically alter the appearance of your tanks. They also may stimulate algae that has been idling along until the new lights go on.

Ideally, look for daylight lamps. Big box stores daylight bulbs will be fine. Daylight lamps are available for the lengths you listed.
Daylight is generally defined as 6500K. Most of us would call 5000K to 10000K daylight - with 5000K being a bit reddish and the 10000K being very white.

My favorite lamps are GE 9325s which are all but gone from the market.