how much light is needed

[saulgonzalez]

i have a 40gal that has a 17watt flouresent tube and feel it is not enough light.as i am growing brown algae i leave it on for about 15 hours a day and the algea is still there.

 

[emo]

17watts for a 40 works out at 0.4 watts per gallon. For most plants you need in excess of 1.5 watts per gallon, i think... someone else can probably give you a better idea. I have about 2wpg and my plants all do well.

As for the beard algae, try cutting down the amount of time you have your lights on for... 15 hours is quite a long time.

I have mine on for a total of 12 hours, using a 'siesta' method. On for a few hours in the morning, then off for a few, then on again till I go to bed.

To get rid of the beard algae i would suggest having your lights on for no more than 9 hours a day till it clears up... try 4 hours on, 3 off then 5 on. Make sure during the 3 hours off you have some diffused light through a window, as the plants make out this is cloud cover, but the algae can't stand it.

I got rid of a bad amount of hair algae over the course of about 2 weeks using this method.

 

[freddyk]

15 hours is already near the limit, you won't want the fish to have too long of a day. If poor lighting is the main reason for your brown algae problem, adding a stronger light is the best alternative.

 

[emo]

Oops, sorry I thought you said beard algae )

Who knows... might work on brown algae just as well?

 

[BigFishSmallPond]

I go 12 n 12 for light 8 am til 8 pm then leave a light on nearby for 30 mins before killing that light too.(minimise instant dark stress) =]

 

[keane]

my main lights stay on for eight and a half hours.

I do 1pm - 9pm with main lights only, then my moonlights kick in at 9 and my main lights stay on with them until 9.30pm.

Then the main lights click off at 9.30pm and my moonlights stay on until about 11.30pm.

This is, like BFSP says to minimise instant darkness.

No algae at all!

steve 8)