Is this enough light for a 29 gallon low light planted tank?

[FastFly67]

The Coralife F/W Aqualight T-5 is a double lamp fixture ideal for freshwater and planted aquariums. Includes one Colormax Full Spectrum and one 6700K T-5 (5/8 diameter) fluorescent lamp. Features an on/off switch, a built in electronic ballast, sleek black aluminum housing, a highly polished reflector, acrylic lens cover and adjustable width tank mounts. T-5 lamps are 18 watts each.

[SpeedEuphoria]

It should be fine for low light plants IMO, but there are better fixtures that would get you around ~2wpg

[FastFly67]

Originally Posted by SpeedEuphoria

It should be fine for low light plants IMO, but there are better fixtures that would get you around ~2wpg

I'm broke.

[gheitman]

That Coralife fixture is a good one (I have the exact same one on a 20 gallon long tank) but I would recommend the slightly more expensive PC fixture with a single 65W lamp. I bought one recently for a 29 gallon tank and it has been perfect. You can find them online at Coralife Freshwater Aqualight Deluxe-Single 30" Strip at Big Al's Online.

[SpeedEuphoria]

If your broke go to lowes/walmart and get 2 clip on lights. You can get the aluminum ones that are for a work light, or the black ones that look better and are for interior stuff.

Then just get 2x 23/26w daylight spiral compact flourescent bulbs and you'll be growing stuff

That should cost you ~$25 and you will be able to grow plenty of stuff

[Carissa]

Since fluorescent lights create more or less effective light due to the shape of the bulb, that has to be taken into consideration when figuring out the wpg. T5's should be multiplied by about 1.2, and the screw in type CF's are about .8.

So with the original fixture you are getting:
18watts x 2 = 36 x 1.2 = 43.2 watts (1.5 wpg)

With the two screw-in type bulbs:
26 watts x 2 = 52 x .8 = 41.6 (1.43 wpg)

So the T5's will actually do you a bit better. If the reflectors are good, you can look at another 50% increase in effective light besides. Going from no reflectors to very good reflectors can increase the light by 90%.

The height of the bulbs from the water surface also makes a massive difference. If you raise your fixture by just a couple inches, you could be getting 25 - 40% less light into the tank. So as you can see there are lots of other considerations other than simply how much power it takes to drive a bulb, which is all that wattage is telling you.

[SpeedEuphoria]

Originally Posted by Carissa

Since fluorescent lights create more or less effective light due to the shape of the bulb, that has to be taken into consideration when figuring out the wpg. T5's should be multiplied by about 1.2, and the screw in type CF's are about .8.

Well not sure where this info comes from, but I do believe that T5's are better, no doubt. Its not just the shape of the bulb, its also the lumens per watt delivered or efficiency.

These 1.2 and .8 numbers. how were they measured? Also the .8 number what orientation of the bulb was used in this test? The bulbs are designed to be used vertical, many aquariums use them in the horizontal position which I believe is less efficient(maybe not). Also since they are larger diameter bulbs you need to use larger diameter reflectors/fittings, which is very hard to do in the horizontal position how many aquarist like myself use them. On the T5's tested what kind of reflector was used? The higher end fixtures have a much better reflector then the Coralife("average" reflector), so that needs to be accounted for also.

They are just guesstimates, just like WPG. If your going to try to get technical you must provide some better information. Your better off using the water depth and surface area to make comparisons. You cannot just say that the T5's will be better based on a simple linear approach for each particular setup. I will say that IMO the tube bulbs or T5's should do better with deeper tanks, the 29G would be the deepest tank that I would consider using screw in bulbs for.

If you are guesstimating you cannot go to decimal points to prove that T5's would be better then what I proposed, you can say that they should be about the same, that's all you can say.

I will say that IMO the coralife fixture and the method I provided would be better for a 20 long then on a 29G. I think the Current USA would be a better fixture for a 29G and non CO2 but again I dont think the bulbs on that one cover the entire width, neither does that PC coralife that was mentioned.

[Carissa]

Here's some info if you want to wade through it....

Light Intensity in an aquarium - Page 8 - Aquarium Plants - Barr Report

Basically what it boils down to is that nothing is exact because there are so many variables - but if you were to take fairly identical setups and change only the bulbs, the .8/1/1.2 multipliers would be within the ballpark of the difference you would see, due to restrike factors. WPG is a very loose term, but it was originally intended to correlate to something along the lines of T8's with decent reflectors. Go to something like a T5 or a screw in cf, and start changing reflectors, all those things have to be taken into consideration when thinking about how much light you're really going to get in practice, and that was my point. Small differences don't matter much to the plants, if someone wanted to save a few bucks and go with the screw-in cf's, that's great. I actually have one tank lit by cf's myself. But based on my understanding of the tests that have been done on them, I don't think it would be accurate to say that they would be getting more light that way, in fact I would be surprised if they didn't perhaps get less, also due to other factors such as (most likely) poorer reflectors, and a greater distance from the bulb to the tank. I wasn't trying to get picky, just illustrating why the wpg rule is only a very general one.

Personally, I've had poor success with the cf's mounted vertically. I think it's because it creates more of a spotlight, so you end up with very high light in the middle (which always created algae for me), tapering off to very low light where the light isn't shining (and poor plant growth). To avoid this, the light can be raised, but this greatly decreases the amount of light you are actually getting, so then you need to increase wattage accordingly. I just found it to be a bit of a pain on anything bigger than a 5g.