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To much light or to much nutrients?

2K views 11 replies 7 participants last post by  AbbeysDad 
#1 ·
I have this algae all over my plants and a little on my driftwood. I have 2 13watt 6500K bulbs running 10 hours a day on my 20 gallon tank. I am also dosing Flourish Comprehensive twice a week. How do I know if I have to much light or to much nutrients?
 

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#2 · (Edited)
That's a good question! Simply put I don't know though I would think it is more to do with too much light in the sense of hours. I would cut back the hours to something like 8 hours a day instead of ten. See if that helps if not you can try cutting back on the fertilizers to once a week but I am honestly thinking it is too much light. It looks like hair algae like I get on my vals near the top of the tank that I get when my lights are on too long or it gets direct sunlight from the window behind the tank if the blinds are open. Which is why I thinking it is a light problem but might want to see what others have to say.
 
#3 ·
Thanks Boredomb. I was also thinking that it is a problem with to much light. The only reason I have th lights on for 10 hours a day is because I believe it was byron that said tropical fish get 10 hours of light, 10 hours of complete darkness, and 4 hours of dusk/dawn. I am trying to mimic the natural environment of my lemon tetra so I thought that would be a good starting point
 
#5 ·

I think it's not the duration, but too much light. Suggested light for plants is 2-3 watts per gallon, for more moderate to high level light plants. Is there a way you can put one light on a timer, so both aren't on for the 9 hours? Algae is the result of too much light, for what can be assimilated by the plants.

Gwen


 
#8 ·
my understanding is that if only one is too much, it wouldn't matter as much. plants, including algae, need both nutrients and light to grow. cutting back either one will probably help, but you could probably cut back on both, have no adverse affects to your plants, and save you some money. i'd go with 8 hours of light and dosing once a week. see what that does. it may do nothing, in which case you can cut back more on one or the other, it may reduce your algae problem, in which case you're set, or it may affect your plants, in which case you can always up either or both again. just keep an eye on your plants and you should be ok.
 
#9 ·
I don't have much to offer here, except you got me thinking...(and since I shut down our fry tank [moved the youngins into the 'big pond'], I have an extra timer)... so I thought, why not better simulate dawn, midday, and dusk. So I setup one of the light sets to come on at 8a, off at 9p and the other to come on at 11a/noon, off at 7p.
 
#10 · (Edited)
Light is always the issue with algae.

Each planted aquarium is biologically different, but the prime goal is the same: balance between light and all nutrients. If this is achieved, plants will utilize the nutrients and light first (they surprisingly out-compete algae when everything is available); as soon as something is missing or used up, algae will take advantage.

Nutrients are 17 in number, and occur from several sources. Plant fertilizer (which can be enriched substrate, liquid or tablet), fish food, organics from waste, source (tap) water. As the latter 3 especially will vary from tank to tank, the balance has to be worked out for each individual tank, though it is possible to work out generalities to some extent.

For those of us with natural (low-tech) systems, the nutrient most often in short supply is carbon, as CO2. This occurs from biological processes in the aquarium, namely fish and plant respiration (both give off CO2 continually) but more importantly bacteria through the breakdown of organics in the substrate. The latter is the largest source of CO2 in planted tanks. We can fairly easily control most of the other nutrients which can, if needed, be added as liquid or substrate fertilizers. But carbon depends solely upon the tank's biology.

Because algae is so adaptable with respect to nutrients and light, it will readily take advantage of any breakdown in the balance. CO2 will usually be the first nutrient to be used up, and plants simply cannot photosynthesize without sufficient carbon. If light is still present, however "dim" it may be, algae will use it. This is why we say that light should always be the limiting factor to plant growth. Once light is stopped, algae cannot increase even if nutrients are present.

The above is the theory; now to the practical in this present issue. I would reduce the light duration. You can go down to six hours and plants will still manage. I have my lights on 8 hours, and algae is here and there depending upon the tank, but not excessive. But the number of hours depends upon each tank's biology, so simply reduce an hour at a time until you find the point when algae does not continue to increase. It will not disappear, what is there, but it will stop increasing. You have 13w CF bulbs; over my 20g I have two 10w CF bulbs, daylight 6500K. It might not seem like it, but changing to the 10w bulbs might make quite a difference. If it were me, I would do this first, then decrease the duration if still needed as I frankly suspect it might, but not as much. The issue with intensity is that plants will use the light provided everything else is available, and photosynthesize to the max; this means the CO2 will be used faster than under less intense light. So less intense light can be slightly longer in duration than otherwise, provided it is still sufficient to drive the plants' photosynthesis.

Last word on the 10 hour point. In the tropical regions, daylight and darkness are equal all 365 days of the year. But when it comes to the aquarium plants, many of which are not true aquatic but amphibious bog or marsh plants, "daylight" can be direct sunlight or indirect light due to the forest canopy shading it, cloud, overhanging vegetation, etc. The only point about this is the periods of light and dark.

Byron.
 
#12 ·
What is also interesting here is our perception of algae. Aside from the negative aesthetics of glass and decor, and the potential negative affect on plants, algae can be a good aid in water purification. Many refugiums encourage algae growth to further purify the water.

If after reducing the light and/or nutrients, if the algae problem persists, perhaps an inexpensive submersible UV sterilizer may be the answer??? (which may also have additional benefits).

Disclaimer: I don't profess to be an expert on the subject as like most all of us, I'm still learning too - I've just been intrigued lately by sump filter setups and discovered that although wet/dry is still very popular, refugiums with [deep] sand beds, plants and sometimes algae are also very popular. Algae in the refugium helps keep it out of the main tank as it purifies water by 'banking' negative elements.
 
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