# big yellow water lettuce vs. small green water lettuce; why?



## Morainy (Apr 21, 2010)

Hi, Everyone,

One of my sons has been doing a project for his science class, comparing LED and fluorescent nano aquarium lighting. One of his experiments has 2 Fluval Specs with identical substrate, water, plants, etc. Plants in both nano tanks are growing surprisingly well.

The water lettuce under the Fluval Spec LED has grown very large but is on the yellow side.

The water lettuce that has the Azoo fluorescent light is smaller and the leaves are darker green.

The water in each tank is the same because every day we empty half of it and add water from an established planted aquarium.

Can you think of why the water lettuce under the LED would be yellow and bigger? Could it be the effect of the LED light versus fluorescent? He wonders whether it's just that in one tank the water lettuce grows faster and depletes the water of nutrients more quickly? Or maybe water lettuce does better in low lighting versus high lighting? (Or other way around?) 

Any water lettuce experts out there? 

Thank you!
Maureen


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## Morainy (Apr 21, 2010)

I should have posted this under plants, lighting. Sorry! A little brain-fogged this morning.


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## CRS Fan (Apr 21, 2010)

Some of the possible reasons could be the intensity of the light, nutrients available in the water column, or Kelvin temperature of the light sources.

Best Regards,

Stuart 

PS. I also moved your thread !


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## 2wheelsx2 (Apr 21, 2010)

If the yellowing is directly under the LED's and then it starts to green, it's due to the focus of the LED's. By its very nature the intensity of the LED lighting will be exponentially greater closes to the centre of the LED. An overhead shot of each tank would be helpful and would be educational for all of us as we follow along in this experiment.


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## Morainy (Apr 21, 2010)

Thank you, Stuart and 2wheelsX2! (And thanks for moving my thread)

2wheelsx2, I can probably email you my son's report when it's finished, which will be in a week or two. He's about halfway through it. It is not science-fair quality, though. That would take months of rigorous investigation. It's part of a class project. Still, he's already made some interesting observations about plant growth, red plant growth, and the water lettuce under 4 different lights.


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## 2wheelsx2 (Apr 21, 2010)

Morainy said:


> Thank you, Stuart and 2wheelsX2! (And thanks for moving my thread)
> 
> 2wheelsx2, I can probably email you my son's report when it's finished, which will be in a week or two. He's about halfway through it. It is not science-fair quality, though. That would take months of rigorous investigation. It's part of a class project. Still, he's already made some interesting observations about plant growth, red plant growth, and the water lettuce under 4 different lights.


That would be cool. As an applied scientist/engineer, my curiosity is always piqued by real life experiments and findings.


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## Morainy (Apr 21, 2010)

This experiment is not scientific. As a class project (everyone else is growing radish seeds) rather than a science fair project, it has a very short time-frame and of course, zero budget. The lights he is comparing are all in the budget range and for LEDs, I don't think the results will be at all applicable to one of the higher quality lights like Reefbrights or anything with Crees. I think his findings will answer the question, "Will the stock light that comes with my $70 or $100 nano tank setup, really grow plants?"

I've been surprised to see that LED lights give a remarkable clarity to the water. As an engineer, you can probably explain why. The LED lights that he has also make plants appear more to the yellow (in an attractive, healthy way), while the 6400 k fluorescents make them appear more to the green (also in an attractive, healthy way). You have to put plants from both tanks under the same light to see that the plants are not different, the lights are.

So far, the experiment is showing that easy and moderately easy plants do grow well under both the nano Fluval Spec LED and the fancier and more powerful but still budget Eheim Aquastyle LED. Of course, they also grow well under fluorescent. In his experiment, the surface water lettuce grew faster under the LED than under the fluorescent and the stem plants below grew more slowly under LED than under the fluorescent, but it's quite likely that the stem plants grew more slowly just because the water lettuce blocked the light sooner. He's now removed the water lettuce to see what happens.

He's finding that under the Eheim Aquastyle 1200 lumen pendant, Elodea grows long but very thin compared to under fluorescent (in the same tank, at the other end). Over time, more of the wisteria leaves turn broad and plain-shaped under this light, while they stay more pointy under the fluorescent. The red plant that he's got in there moves towards the green under both fluorescent and LED, but when I tried that plant under the more powerful Hagen Glo, it used to do that, too, so there's no surprise.

I was expecting the Eheim Aquastyle to outperform the Fluval Spec light, but there's no evidence of that as long as the Spec is over the narrow, small tank that it was designed for. In fact, at least the elodea is not getting stringy under it. However, in terms of appearance I think many aquarium hobbyists would enjoy a light that is brighter, and might switch to a different small fixture if they can find one. The Eheim's light, by comparison, appears very bright for its size and it is stunning. Plants are doing fine under it. However, so far at least, the Eheim light is not doing as well for elodea, and the difference is quite dramatic. It's so dramatic that elodea that is rooted under the LED but is long enough to be carried on the current toward the other end of that tank, will produce bushier stems that look like the fluorescent side of the tank. I'm not sure why elodea is so different from the other plants, but it may be because the Eheim light is a pendant and therefore some of the plants will not be directly under the light, which seems to matter more for LED than fluorescent.

Based on this nano tank experiment so far, as a hobbyist I would say that these little LEDs and attractive tanks are very good value. Serious aquascapers would keep the tank and upgrade the lights. But this experience has also made me much more interested in getting an upper-end LED light, something I'd never considered before. One thing to keep in mind is that the budget LEDs on the nano tanks probably weren't designed for plant growth. When we contacted Hagen, they didn't even know the specs for their fluval lights and had to run a test using a colour meter. Top end LED lights are custom designed for plant growth and you can even get some for different kinds of setups.



2wheelsx2 said:


> That would be cool. As an applied scientist/engineer, my curiosity is always piqued by real life experiments and findings.


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## 2wheelsx2 (Apr 21, 2010)

Have a look at my ADA cube thread and the Aquaray light tile I'm using. I am injecting CO2 in it though as it would be way too much light without CO2. I am super pleased with it. I am in agreement with you. Prior to this, the best ones I had were the Marineland ones and they're ok, but well designed ones like the AquaRays are amazing. The AquaRays use 3 w Crees.


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## Morainy (Apr 21, 2010)

Your ADA cube is gorgeous! A very interesting thread to follow, too. It's interesting that you didn't get the same results with EcoComplete and Excel that you got with CO2 and ADA.


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## 2wheelsx2 (Apr 21, 2010)

Morainy said:


> Your ADA cube is gorgeous! A very interesting thread to follow, too. It's interesting that you didn't get the same results with EcoComplete and Excel that you got with CO2 and ADA.


Thanks Maureen. I think it's more the CO2 than the ADA AS. But the ADA AS certainly made my life a lot easier. For smaller tanks, I'll never go with anything else again. It was ridiculously easy to achieve great results with ADA. You can do it with anything if you put enough work in it, but with ADA, it was plenty much plant, turn on the lights and CO2 and walk away.


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## Morainy (Apr 21, 2010)

I'm very surprised to hear that! For some reason, I thought that ADA would take more work, and of course that CO2 would be far beyond me.


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## 2wheelsx2 (Apr 21, 2010)

Morainy said:


> I'm very surprised to hear that! For some reason, I thought that ADA would take more work, and of course that CO2 would be far beyond me.


In fact, it's the opposite. People always start by upgrading the lights when in fact, you can grow just about anything easily with CO2 and ADA (or another enriched substrate). A lot of today's algae problems started when PC and then T5HO lights came along, making it a lot cheaper to put an awful lot of light into a tank. In the old days with a single T8, people rarely ran into massive algae problems.

With the right equipment, CO2 is actually very easy. The key is to limit the light to manageable levels. For instance, lighting a 75 gallon with 2 48" (totally 108 w) of T5HO light and ADA AS, you can grow just about anything you want. But some people like to see rapid explosive growth so they go to 4x 48" tubes, which is great if you like pruning and maintenance (I don't). When the maintenance is dropped and the bulbs get too old, the plant mass goes up (thereby decreasing available CO2), one problem surfaces after another. I went through this with both my 20 gallon and my 125 gallon and am never doing that again. That's why I am only doing high light in my ADA cube. Even though it's relatively high light, its tiny size allows me to do 5 - 10 minutes of maintenance a day and be done.


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## InfraredDream (Jun 24, 2010)

So interesting! Thanks a lot, Maureen!


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## Ursus sapien (Apr 21, 2010)

I'm a little late to the party on this thread, but... water lettuce is heat and humidity sensitive. I know, sounds odd for a floating plant, but under the lights indoors the plant can get too dry, leaving it suseptible to yellowing and spider mites.


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## Morainy (Apr 21, 2010)

Thanks, Storm!


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