# High light no CO2, what are the issues



## lauraleellbp

Light is what tells plants how fast to grow. "Low light" plants doesn't mean that they can't or won't grow just as fast under higher light levels than "high light" plants, it just means that they are more tolerant of lower light levels and can survive them whereas "high light" plants often cannot.

Under higher light, since plants are triggered to grow more quickly, they need more nutrients to support that growth. They will very quickly use up what little are provided by the livestock in the tank, and then start developing deficiencies. So it's not just algae you'll have issues with- the faster-growing plants also will basically start dying of "starvation" as well.


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## Fishly

It's best to think of CO2 as another macronutrient instead of as a bonus. To give your plants high light without CO2 is like putting someone on an intense exercise regimen without adding extra carbs and protein to their diet- not only will they not improve, they will deteriorate.


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## Frogmanx82

Thanks for the input. I will back off to 2 watts per gallon which should be less stress on the plants.


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## lauraleellbp

2 wpg with what fixture, though? If you're running T5HO over this tank, for example, 2 wpg will still very much be "high light"...


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## Frogmanx82

I have 3 T6 bulbs at 35 watts each.


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## lauraleellbp

Do the bulbs have individual reflectors?


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## Gatekeeper

Co2 is a major ingredient for photosynthesis. Depriving means undernourished plants. Period.


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## Frogmanx82

Its a twin bulb unit with a single reflector and and single bulb unit, obviously with a single reflector. Not nearly as high tech as my reef lighting.

How much CO2 will guppies, shrimp and snails contribute? Those snails easily number in the hundreds and the shrimp are heading there.


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## lauraleellbp

Try it and see, but I suspect you're probably going to either find a way to limit light and/or dose Excel. You're on the upper end of "low light."


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## Frogmanx82

I'm leaning toward dosing excel. I have a fluorite substrate with a thin layer of pebble over the top. Will I need other ferts?


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## lauraleellbp

Depends on your plants, but I suspect you'll need to supply at least some additional nutrients. Rosette plants like Crypts would probably make do with root tabs.


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## cjacob316

i want to come back to this, let me see if i have this correct

the ammount of light determines how much photosynthesis occurs correct?
photosynthesis uses up nutrients such as nitrates and CO2 correct?
the higher the light and the longer it's left on, the more nutrients it uses up?
is balancing the light and nutrients more important, or increased light and nutrients?
can plants survive on short periods of high light, as long as nutrients are avaiable and not exhausted?
do fish provide enough nutrients for plants, or are other things needed?
how do you keep algae from taking over?


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## mikeb210

cjacob316 said:


> how do you keep algae from taking over?



Balance. That is how you keep algae from taking over. Here is a good link that explains it well.

http://www.aquaticcommunity.com/plants/balanced.php


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## cjacob316

great article, exacctly what i needed, and definitely gives me the exact approach i need to take


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## Frogmanx82

I'm still confused about the affects of longer lighting periods of lower wattage lighting vs shorter periods and higher wattage. Is it true that plants that require high light need a certain intensity that will not be made up by running lower wattage lights for longer periods?


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## Byron

Aquatic plants all require light that is adequate in intensity and duration to allow the plant to photosynthesize. Increasing the duration of light that is of insufficient intensity will not compensate, and neither will the reverse.

Byron.


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