What's the shortest photovoltaic period you've ever held daily on a plant tank?

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dereks

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Mar 7, 2006
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29 gallon, two 18 watt (36 watt total) 6700k t5 bulbs.

Ferts, co2, and excel organic carbon.

If I wanted to increase my lighting should cut back my photovoltaic period from 8 hours maybe down to 6?

What's the shortest period you've used?
 

dougall

...
Mar 29, 2005
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I think I have done maybe 5 in the past.. but it really isn't ideal.

It is really going to depend more on the type of plants you are keeping, and if you are adding anything extra to the aquarium for the plants.

But, personally, I have used 2 T5HO bulbs (39W) over a 36g bowfront aquarium (so same width and I think height) without any issues, nothing was added to the aquarium (ferts or CO2) and maybe a 9 hour photo period.but the load of fish was pretty small so no nitrates to write home about.

The answer is also going to depend on the fixture, used, especially with florescent lights.. the reflector can have a huge effect on the amount of light getting into the tank.


Honestly, my personal preference would be to go with an LED light, you will likely be able to better control the color of the light (CRI or temperature, whichever metric you prefer) and dim the light if needed too. It is going to be preferable to stop algae growing by either reducing the amount of light or adding nutrients/CO2 to the aquarium rather than shortening the photoperiod to 6 hours... Your plants will be starting to suffer at that point.
 
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FreshyFresh

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Jan 11, 2013
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Joel
I've got the same lighting over my 29g and they run about 8-9hrs/day. Various anubia, java moss, java fern and a sword in this tank. Substrate is a very fine natural colored gravel. Almost like a coarse sand.
 
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dereks

AC Members
Original poster
Mar 7, 2006
444
10
18
I think I have done maybe 5 in the past.. but it really isn't ideal.

It is really going to depend more on the type of plants you are keeping, and if you are adding anything extra to the aquarium for the plants.

But, personally, I have used 2 T5HO bulbs (39W) over a 36g bowfront aquarium (so same width and I think height) without any issues, nothing was added to the aquarium (ferts or CO2) and maybe a 9 hour photo period.but the load of fish was pretty small so no nitrates to write home about.

The answer is also going to depend on the fixture, used, especially with florescent lights.. the reflector can have a huge effect on the amount of light getting into the tank.


Honestly, my personal preference would be to go with an LED light, you will likely be able to better control the color of the light (CRI or temperature, whichever metric you prefer) and dim the light if needed too. It is going to be preferable to stop algae growing by either reducing the amount of light or adding nutrients/CO2 to the aquarium rather than shortening the photoperiod to 6 hours... Your plants will be starting to suffer at that point.

Ok I think I see what you're saying. You mean the algae prevention is more about getting the plants to take in the nutrients vs the algae?
 

dougall

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Mar 29, 2005
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There is balance with growing plants.

Nutrients, light and CO2.

All will be there, and there are multiple nutrients.

But basically if something gets too low, it is imbalanced, and algae will be better able to grow.

If you have less light, less CO2 or nutrients will be needed, so there is less chance of algae. But plants requiring higher light will not grow.

If you have more light, more CO2 and nutrients will be needed, if The plants cannot use it well enough, you run the risk of algae being able to use the nutrients that are available to grow.

Basically, if you have more light than the system can handle, you are likely to grow algae rather than plants. lowering the amount 9f light is easier than adding Cow and ferts.
 
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FreshyFresh

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Jan 11, 2013
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Joel
Ok cool. And by the same, do you mean the two 18w, or the four 18w that I've been considering adding?
Mine is a twin tube (two 18w lamps) Odyssea T5HO I bought "open box" off ebay some years ago for cheap. I've been using odyssea or other no-name mail order 6500K color-temp range 18w replacement tubes that I mail order. I try to swap at least one tube at a time every 6-8 months, but I loose track on that.
 
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