I'm trying to figure out what the per watt equivalence is between LED's and other types of lighting. I am actually looking at using them on a freshwater planted tank, but I can't figure out how much would be enough.

I am looking at some of the LED flood lights like the ones available at Home Depot. The PAR 20 bulbs are like $30, and they have some PAR 38 bulbs as well. They are the perfect color temp for a planted tank, but having too much light can cause problems in a planted tank without compressed CO2 injection, which I will not have for now.

Watt for watt, what are these LED bulbs equivalent to? Does anyone know?


And for reference this is what I'm talking about:

LEDs are not really being used in FW due to the expense, I dip my hand in both and to be honest only a few FW enthusiasts are even using T5s, it is a pitty but most FW people use halides, Sodium, or standard output flourescent. I think it would work without a question, not using CO2 is kinda like not dosing calcium, depending on the plant it may or may not grow. I would suggest some easy crypts or swords if you plan on overdriving the tank if you want low light just do Java or Anubias, I think it would look great.

It's going to depend a lot on the size of your tank. I'd start small and work up from there. Being able to adjust your lamp height will help a lot.

Thanks for the input guys!



I will be running CO2. Just not compressed CO2. It's just going to be a 2.5 gal tank for now with a yeast bottle DIY CO2. When I can afford it I will get pressurized CO2 and move everything into a 20 long. And as far as cost I like the fact that they will last me for a decade. It' $29.99 for a PAR 20 bulb and I'm thinking that might be overkill.



Start with a smaller bulb you mean? I think the PAR 20 is the smallest one that will run on AC, and finding a DC fixture to go over a 2.5 gal tank may be a challenge. But good point about moving it up and down.

Any idea how much light a PAR20 or 38 bulb puts out compared to something like a CFL, PC's, T5's etc... I don't even know what ballpark I'm in here.

it depends on the bulb the par size only refers to the size of the bulb i think
depends on what plants you are keeping but id say one is enough for plenty of light

If you can get a PAR20 with wide-ish optics (60 or greater), then it should work pretty well. You may have to mount it 12-16" off the water to get coverage, but PAR should be similar to the PC you were running. You could go with a bigger lamp, but you will have to raise it more. The advantage is greater coverage though.

I wasn't running a PC, or any light yet. I'm still in the process of setting up this tank. I just need the light and a fixture to run it in.

I did find a 2.4 watt LED desk lamp at Wal Mart though that says it puts out the same as a 13 watt CFL or a 60 watt incandescent. I think that might be perfect for a 2.5 gal planted tank anyway. Any thoughts on that?

The freshwater hobby is still stuck on watts per gallon, but anything over 2 watts per gallon is considered high light, and with a 13 watt equivalence I would be at 5.2, so I think I would still need to raise it pretty high. But lamp with the 2.4 watt LED bulb is only $19.99.

wpg breaks down for anything smaller than 20ish gal
id say a 2.5 would have to have at least 9w cfl to be medium light.
i have 40w over a ten gal that i consider med-high

So this LED that is equal to 13 watts should be perfect for a medium-high light right?

For $20 including the fixture I'm really leaning towards it. The only thing is I can't tell what the color temp of the LED will be. But for a planted tank I think color temp is a lot more subjective.

id stick with easier plants first, and test your limits

I'll throw in a bunch of "starter" plants, but I also want to go for a nice carpet of HC or maybe Utricularia graminifolia.

But my stocking list includes some easier plants like java fern, maybe java or xmas moss (haven't decided yet), a few types of anubias, etc...

For about $15 shipped I can get all of the following:

Amazonicus x 3
Anubias Barteri Golden
Anubias Barteri nana
Anubias Nana "mini"
Echinodors Fantasi
Echinodorus Uruguayensis
Fissidens Fontanus +Driftwood
Glossostigma elatinoides (glosso)
Java Fern
Microsorium Pteropus Semi Narrow
Rotala
Windelov Java Fern
Xmas Moss








Also, this is not my first planted tank. I had a planted 55 before I got into salt water. I've just started getting that itch again

Try the 2.4W lamp and see how it works. Don't use those comparisons the manufacturers state as an acurate guide though. It's all marketing crap. What you should be worried about is spread and color right now. If it's using 5/8/10mm LEDs then there is a chance the color temp is a little on the high side. For $20, it might be worth a try.

I'll buy it tonight and then take some pics. I'm sure you know a lot more about LED's than I do. You are the LED gawd after all.

What's sad is that the "LED gawd" is still running spiral PCs over his planted tank. I swear, that tank is more work than all of my reefs combined.

OK, here's what I got.


This is with the light raised. you can see that it has a good spread and doesn't do the spotlight effect.


Even with it lowered to the top of the tank the bottom of the tank gets full coverage.


This is probably about where I would run it if I keep this fixture.


And the bottom view of the fixture



And it's reading at about 4500K. Maybe even as high as 4800 or 5000K. But at least 4500 for sure. This is slightly more yellow than a perfectly ideal setup, but I think it's a livable situation for sure.

Any input on this?



Yeah, I know my old planted 55 was more work than my reef tank. And almost as expensive. The water changes were at least free.

Looks decent. Only time will tell if it will work well.

Good point. now I'll ahve to get my hardscaping done so I can add some plants!

I was curious... So I took a pic of it at 1600 ISO, f/5.6 and a 1/30 of a second. This is what I got:


I also added some weeds from the yard to see what they would look like under the light. I'm happy with the coloration.


I then took a pic of my reef tank at the exact same camera settings (1600 ISO, f/5.6 and a 1/30 of a second) and the exposure was darker. So this tank is lit more than my reef tank with 2X T5 HO's. I was both surprised and pleased to find that the lighting in this tank is greater than the lighting in my reef tank.


The difference in exposure was about 2 stops, which means that these LED's are providing ~4 times more light than my T5 setup on my reef tank!!!

Don't know about that. The intensity change you see is because of the sensitivity of the image sensor to red. The sensitivity curve on camera sensors is very similar to the eye, so blues are not picked up as well. The LEDs may look brighter, but the relative intensities are much different. Believe me, the T5s are generating a lot more usable light.

Interesting.

To really test that out I'd have to take images of a gray card under the different lights. I'll give that a try when I can find my gray card. Not that it matters though. I think I'll be fine for a planted tank, and like you say, there's only one way to find out for sure.

Yup. That could work pretty well for a low tech pico planted tank.