# Why is too much light bad?



## jcgd (Feb 18, 2004)

Because you can't feed the tank enough co2 --> easily. It's too hard to balance everything, including not suffocating your fish. 

It's better to have low light with co2 if you want a trouble free tank.


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## Wasserpest (Jun 12, 2003)

Light makes plants photosynthesize, which leads to growth. More light results in faster growth. To grow (build substance) plants need nutrients. CO2 was mentioned, also macro and micro nutrients. If they are all available in adequate levels, then a lot of light is not bad. Too much light is bad because you are implying it would require nutrient levels that are too high to maintain.

The other side of the coin is that light requires energy. So if you just blast your tank with light, you will be wasting a lot of energy. This is bad for a variety of reasons.


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## nokturnalkid (Apr 3, 2007)

jcgd said:


> Because you can't feed the tank enough co2 --> easily. It's too hard to balance everything, including not suffocating your fish.
> 
> It's better to have low light with co2 if you want a trouble free tank.




+1. The problem isn't how much light you have, it is how much co2 you can inject into your tank while not killing the inhabitants.


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## roadmaster (Nov 5, 2009)

Light drives everything in planted aquariums.
More light means plant's need more nutrient's /CO2.
Too much light and not enough CO2/ nutrient's. = poor plant performance but splendid algae growth IME.


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## DrMiller357 (May 16, 2011)

So basically its not "bad" its just not efficient, alright that makes sense, but what about algae doesn't too much light promote algae growth?


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## nokturnalkid (Apr 3, 2007)

Too much light only promotes algae growth when there is an imbalance. Ferts is easy to rule out by dosing with ei. It comes down to not being able to supply enough co2 to support the demand of high lighting. In a farm tank without any fauna, you can have high light without algae. It's easier to pump in lots of co2 without fear of killing fish or shrimps.


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## Sierra255 (Sep 13, 2007)

Algae feeds off of an imbalance between light, nutrients and CO2 available. As others have said, the more light you have, the more nutrients and CO2 your plants will need. If there is an infinite amount of light, there will be a limit as to how much CO2 and nutrients the plants can use up in a given time. Algae will then start to feed off of the excess. Everything needs to be in balance in order to have an algae free planted aquarium. That's why more light is not always better.

Look at the relationship like this. If you were provided a buffet all day every day (and you need a drink (nutrients and CO2 in a planted tank) to wash it all down, therefore the more you have to drink, the more you can eat), there will be a limit to how much you can eat each day, even if there is an unlimited supply of drinks. If the food is brought out in large quantities all day long (extremely high light), there will be a lot of leftovers, a perfect environment for things to start going bad. Also, the longer the leftovers sit out before being consumed, the greater the chance of it going bad (algae growing). However, if you have the number of drinks you require for the day at the beginning (remember, these are the nutrients or fertilizers, including CO2) and the food is made and brought out to you more slowly to match your eating pace, the food is all consumed and none of it goes bad. Same basic idea in a planted aquarium. There's no gorging early on in the day, but instead everything is in balance. The light level (and length of time it's on) is in balance with the nutrients available (fertilizers and CO2) so nothing goes to waste.

Hopefully this analogy will help to explain the balance that's required to have an algae-free planted aquarium and didn't just confuse the heck out of anyone.


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## becks17 (Dec 21, 2009)

Algae are more capable of using carbonates in the water as a carbon source. Your plants can only use so much of the light with limited CO2, the rest is just "feeding" the algae.


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## BBradbury (Nov 8, 2010)

*Planted Tanks*



DrMiller357 said:


> Im new to planted tanks and just want to clarify this, why is too much light bad?


Hello Dr...

You could go the "low tech" route and just use standard, flourescent bulbs. Lighting really wouldn't be an issue. The local hardware stores carry GE aquarium plant bulbs for a few dollars. A couple of T8s or T12s, 6500 K, will grow the majority of aquatic plants quite well. Just match the lighting to the particular plant or plants. You don't need more than a couple of watts of light per gallon of tank volume. A lot of plants don't require even that much.

I've used them for years in my large, planted tanks and with some very inexpensive ferts, you can have a real jungle in the tank in a matter of a few months.

Attached is a pic of one of my tanks. I just use some pots with a little potting mixture and pea gravel. The tank has just a single bulb for light.

Planted tanks are really very easy.

B


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## roadmaster (Nov 5, 2009)

nokturnalkid said:


> Too much light only promotes algae growth when there is an imbalance. Ferts is easy to rule out by dosing with ei. It comes down to not being able to supply enough co2 to support the demand of high lighting. In a farm tank without any fauna, you can have high light without algae. It's easier to pump in lots of co2 without fear of killing fish or shrimps.


Too much light creates the imbalance you speak of, (ie) not enough nutrient's and CO2.
Back off the light,and less nutrient's and CO2 are needed.


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## DrMiller357 (May 16, 2011)

Thanks for the explanation sierra255 I think i understand it now.

My current setup: 40g(L 36", D 18", H 16") I got a vanity light from a garage sale and made a housing for it, it has 6 6500k 18watt CLFs which I'm sure is way too much light it runs for 10hours and it has some miracle grow with play sand on top. I don't have any CO2 but i did buy some flourish excel yesterday. I've got a ton of guppys and some dwarf puffers in there now. Its not a newly set up tank, but i added the light, miracle grow, and some plants about a month ago. Plant growth has been amazing but over the past few days algae has gone out of control.

What would you guys suggest I do to put my tank in balance? Will Flourish excel be enough as far as CO2?


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## Hoppy (Dec 24, 2005)

I don't think it is a balance that is important. It is keeping the plants growing in good health, which requires that they have enough of all of the nutrients needed to maintain the growth rate the light intensity drives them to. With high light it requires such a high level of CO2 that it is hard to maintain that without gassing the fish. Take the fish out, and jack up the CO2 concentratiion to 100 ppm or more, and I suspect you could keep the plants growing very fast with minimal algae problems.

However, you still have to keep the tank clean, the water clean, the filter clean, maintain very good water circulation in the tank, and good dissolved oxygen level in the water, plus pruning away any dead, dying or unhealthy leaves as soon as they show up. A small mistake with high light can quickly become a disaster, even with high CO2.


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## Hoppy (Dec 24, 2005)

DrMiller357 said:


> Thanks for the explanation sierra255 I think i understand it now.
> 
> My current setup: 40g(L 36", D 18", H 16") I got a vanity light from a garage sale and made a housing for it, it has 6 6500k 18watt CLFs which I'm sure is way too much light it runs for 10hours and it has some miracle grow with play sand on top. I don't have any CO2 but i did buy some flourish excel yesterday. I've got a ton of guppys and some dwarf puffers in there now. Its not a newly set up tank, but i added the light, miracle grow, and some plants about a month ago. Plant growth has been amazing but over the past few days algae has gone out of control.
> 
> What would you guys suggest I do to put my tank in balance? Will Flourish excel be enough as far as CO2?


How much light you have depends on whether or not those CFL bulbs have good reflectors or not, and whether they are mounted horizontally or vertically over the tank. And, the amount of light you have drops roughly proportional to the distance from the lights to the substrate squared. (At 10 inches the light intensity is 4 times as high as it is at 20 inches.)

So, can you describe your light fixture better, and post a photo of the bulbs in position in the light? And, does it sit directly on top of the tank or is it suspended some distance above the top of the tank?


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## DrMiller357 (May 16, 2011)

The cfls are mounted vertically but has little reflection(just the lightly colored wood casing), they are 2 inches above the water and 15 inches from the substrate. I will try and post a picture if i can find the memory card for my camera.


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## pejerrey (Dec 5, 2011)

Besides the joke above, IMO it's easier to have low light because the tank "metabolism" possibly needs less inputs. I mean ferts, co2, water changes, trimming cleaning glass, fight algae, etc. The catch is that you may not be able to grow whatever you want but you will still have a few nice things to grow besides Anubias and moss.

In my experience:

Inert substrate+ High light +ferts+lot of co2+weekly 30% water change and trimming + never ending algae bloom.









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Inert substrate+low light. No ferts, no co2, no algae blooms. 25% gal Water change every 2 months, no trimming yet, no glass cleaning yet. Few months old.


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## DrMiller357 (May 16, 2011)

Yea i will probly lower my light, i dont think im growing anything that requires high light. But would like to try at least for awhile to see how it goes.

Funny pic, and funny you mention it, there has been a van parked outside my house for a month, around the time i upped my lighting on all my tanks. I have to check for bugs. :hihi:


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## vincenz (Jan 29, 2012)

BBradbury said:


> Attached is a pic of one of my tanks. I just use some pots with a little potting mixture and pea gravel. The tank has just a single bulb for light.
> 
> Planted tanks are really very easy.
> 
> B


Holy moly, are those endlers?


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## herns (May 6, 2008)

Hoppy said:


> How much light you have depends on whether or not those CFL bulbs have good reflectors or not, and whether they are mounted horizontally or vertically over the tank. And, the amount of light you have drops roughly proportional to the distance from the lights to the substrate squared. (At 10 inches the light intensity is 4 times as high as it is at 20 inches.)
> 
> So, can you describe your light fixture better, and post a photo of the bulbs in position in the light? And, does it sit directly on top of the tank or is it suspended some distance above the top of the tank?


+1. Hoppy have always good insight on lightings.:thumbsup:

I use high light as noon burst 2-3 hours. if it doesnt grow algae, I add another hour or so.


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## DrMiller357 (May 16, 2011)

That sounds like a good idea herns, if I buy another pack of timers and do some rewiring I could set somthing like that up. I could even go for a 3 stage 2 bulbs every few hours, first set 10am-10pm, second set 12pm-8pm, third set 2pm-6pm. What do you guys think, how would you do the hours?

Here is a pic of my light, took it with my webcam sry for the poor quality. It makes my tank look much brighter than it really is.


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