# FloatingPlants/Algae Control



## dwalstad (Apr 14, 2006)

Hello Everyone,

I have long advocated floating plants and emergent growth to control algae (my book, Chapter IX), as these plants have several advantages over algae. However, I left out a crucial part-- the role of daylength in getting these plants to grow well in your tank. 

I stumbled on the way to get these plants to grow and control algae just last month when I set up a breeding tank. I kept a trio of Rainbowfish alone in my 55 gal for 10 days. After I removed the fish, the eggs started hatching. I've now got 100's of babies. To avoid the hassle of catching them, I decided to keep them in the 55 gal and try raising them in it.

Baby Rainbowfish like high temperature and still water. They'll die if there's too much water current, so I shut off the filter completely. I put a second heater on the very bottom of the tank to warm up the bottom layer of water and encourage convection currents. After all, the 55 gal is a very tall tank. I also decided to increase the daylength for reasons described at the end of this post. I increased the daylength from 12 hr to 15 hr a day. The amount of lighting (80 watts plus full Northern window light) stayed the same.

In the meantime, this tank also had a bad case of algae- gobs of greeny, fluffy matting all over the floating Water Sprite, which wasn't doing well (yellowish leaves and rotting roots). If I added floating FrogBit to the tank, it would die.

Well, folks, within weeks, the Water Sprite and Frog Bit "greened up" and took off. I now have a solid mass of beautiful floating plants on top. The algae has started disappearing; a mat of it that was stuck to the back glass actually peeled off. Stem plants shot up to the surface growing maybe an inch a day. 

The baby fish are doing great and growing fast. It's lovely when everything works out without any work! 

Some background on promoting emergent growth and floating plants: 


Christel Kasselmann, author of the excellent book 'Aquarium Plants' pointed me in the right direction. Her article in the latest TAG ('The Aquatic Gardener', vol 20, no 4) described how she could get her small water lillies (Nymphaea micrantha) to stay submerged if she used a 12 hr photoperiod. If she used a longer photoperiod, she got floating leaves, flowers and reproduction.

Then I remembered that emergent growth is stimulated by summer conditions-- high temperature, good lighting, AND a long daylength (12 hr/day is not enough!). These summer conditons trigger emergent growth; its a "hormonal thingy" for aquatic plants that is "hard-wired" into the plant. 

I found that I could get good emergent and floating plant growth in my tank with lights on 15 hr per day instead of 12. 

Lastly, since we're talking about daylength, Christel Kasselmann also writes that 8-10 hr per day of daylength "may lead to a considerable loss of plants". She recommends a minimum lighting period of 12 hr (her book, p. 51). I would agree with her; she's an expert.


----------



## newbie314 (Mar 2, 2007)

This is very interesting information.
I've used 12hours/day from the start. Even for the small tank with 4W/gallon.
Makes me feel better since it's a lot of people use 8-10hours.

The two reasons were:

I assumed tropical would be about 12hours per day (at the equator) 
And more importantly I wanted to see the tank in the morning while having my coffee and petting my cat, and to be able to see it when I came home in the evening.
So a question arises:
Does this mean having a higher than 2-3 Watts is better for emergent growth? It is an increase in light energy. My 2.5 gallon has always been a little high but lot of growth especially duckweed (which died due to java moss choking the roots - replaced DW from big tank)
- after a little more thought I guess this isn't always the case as the plants can only process so much light. But it will heat the tank some and allow for more plant growth on the bottom

As for duckweed, I thought it doesn't flower unless it's cool out, early spring like. The duckweed I assume is considered a more temperate plant.


----------



## Dzidek1983 (Dec 13, 2007)

i have a 20 inches high tank and 108W in my 64 gallon tank... the light is 10 hours a day with a 2 hour period with no light at midday...

my floating plants are doing great, Pistia is now covering the whole tank, with her roots being about 15-20 cm long 

what is more interesting... in a particular place in my tank, that Pistia didn't cover i noticed more algae growth, especially long green algae, and green dust on the glass... the covered side of the tank was almost clear from this algae... 

does this mean i have to much light? or maybe wrong combination of light bulbs... i don't have the red "plant bulbs"

well.. at this time Pistia is already covering the whole tank and i will see if it helps on the algae


PS. today when i was planting my nymphea rubra, some of the soil got to the water (my mistake, i should cut the roots, not tear the whole plant out)... i vacuumed the soil out of the tank... will it affect algae growth?


----------



## dwalstad (Apr 14, 2006)

newbie314 said:


> Does this mean having a higher than 2-3 Watts is better for emergent growth?
> 
> ***Probably, since emergent plants (unlike submerged plants) can use intense light. However, I don't think its necessary. Remember that emergent plants are getting all their light from the surface, so all the watts/gal rules don't apply. For example, I now have 80 watt of light (two 40 watt bulbs- one cool-white and the other full-spectrum) over my 55 gal (4 sq ft surface area), which is 1.4 watts/gal. However, when I had the same lighting over my 33 gal (also 4 sq ft surface area), I had 2.4 watts per gallon. Although the watts/gal was different, the emergent plants were getting the exact same amount of light.
> 
> ...


----------



## ItsDubC (Jan 12, 2008)

Is daylength the total number of hours that plants receive light, or the difference in hours between when lights first come on in the morning and when they shut off at night?

The reason I ask is because I am currently dealing with an algae issue, so I have my lighting schedule staggered in an attempt to control it: lights on for 4hrs starting at 6AM, lights off for 1hr, lights on for 5hrs, lights off for 1hr, lights on for 2hrs until 7PM. So in this case, is my daylength 11hrs (4+5+2) or 13hrs (6AM-7PM)?


----------



## Dzidek1983 (Dec 13, 2007)

it's the total number of hours that plants receive light... f.ex. my light is on from 10 to 14... then 2 hours break, and from 16 they are on until 22... so in total there is 10 hours of light... 

i heard that a break at midday is good, it simulates tropical rains


----------



## Revernance (Aug 20, 2007)

Hornwort, cabomba, and anacharis float but can they utilize co2 from the air? (I see only a few leaves sticking out of the water line)


----------



## Red_Rose (Mar 18, 2007)

Revernance said:


> Hornwort, cabomba, and anacharis float but can they utilize co2 from the air? (I see only a few leaves sticking out of the water line)


I think if they can be grown emergent then yes but I think those plants are the type that can only be grown submerged. I currently have some H. difformis in my new tank floating and some of the leaves are out of the water. According to the PlantFinder, this plant can be grown emergent so I think it's safe to assume that it's getting CO2 from the air.


----------



## Revernance (Aug 20, 2007)

Red_Rose said:


> I think if they can be grown emergent then yes but I think those plants are the type that can only be grown submerged. I currently have some H. difformis in my new tank floating and some of the leaves are out of the water. According to the PlantFinder, this plant can be grown emergent so I think it's safe to assume that it's getting CO2 from the air.


I think you're right. That makes sense. 
Even if some floating plants can't utilize co2 from the air, at least they can get better access to light by being at the top.


----------



## Red_Rose (Mar 18, 2007)

Revernance said:


> Even if some floating plants can't utilize co2 from the air, at least they can get better access to light by being at the top.


That's true. I get my Hornwort at PetsMart and they have it planted in gravel. Although it does look nice, when you leave it as a floater, it grows even better and the plant looks like a brighter green whereas when it's planted, it looks more duller, IMHO.


----------



## newbie314 (Mar 2, 2007)

Hmm. Never have grown my hornwort floating.
They look nice in the soil though.


----------



## Revernance (Aug 20, 2007)

Red_Rose said:


> That's true. I get my Hornwort at PetsMart and they have it planted in gravel. Although it does look nice, when you leave it as a floater, it grows even better and the plant looks like a brighter green whereas when it's planted, it looks more duller, IMHO.


well at least your petsmart sell hornwort. mine sells the corpse of hornwort.


----------



## fjf888 (Dec 4, 2007)

On my new NPT I was having problems with the floating plants, hortwort and duckweed were not doing great and most of my stem plants melted (ambulia) with the stock 8W t-5 in my eclipse 6. I had it running 14hrs/day. I replaced the 8W with a 27W desk lamp 6500k color, and kept the light time at 14 hours. Growth has taken off an my water has cleared up, although the 50% water change and tripling the carbon probably helped as well.

However, I think the primary kick start to better plant health and growth was the additional light intensity along with the 14 hr duration. Without the necessary light intensity running the lights a long duration is just a waste. Tank still has no visible algae and its been up for a about a month now.


Fred


----------



## newbie314 (Mar 2, 2007)

Interesting.
I have the 10W eclispe 5500k over my son's 2.5.
Things are growing but not too fast and duckweed is at a standstill.
The bulb is 1year old.
I think duckweed is a great indicator of light level. 
I assume also nutrients so maybe that is the issue (less nutrients in teh water column).

The vals are growing and I believe that is due to crab food and algae wafers.


----------



## Revernance (Aug 20, 2007)

newbie314 said:


> Interesting.
> I have the 10W eclispe 5500k over my son's 2.5.
> Things are growing but not too fast and duckweed is at a standstill.
> The bulb is 1year old.
> ...


I believe I heard somewhere that light loses their intensity after about 6 months.


----------

