Lighting duration and intensity

> From: George Booth <booth at hpmtlgb1_lvld.hp.com>
> Date: Mon, 10 Jul 1995 09:04:51 -0600
> Subject: Lighting: Duration vs. Intensity
> If the plant FAQ has duration as part of the formula, I would discount
> it's usefulness.  You can't make up for low intensity by leaving the
> lights on longer.  

The FAQ has a simple formula to calculate the "watt-hours". It implies 
you can increase the hours to compensate lower wattage, upto 16 hours a 
day. After that, it says you must increase wattage.
> > In a recent post, George Booth said that he only kept his discus tank
> > on 9 hours a day due to algae problem.
> Karla mentioned that it's really 10 hours/day if you count the hour
> the lights are on in the morning for feeding.  Also, there was not an 
> algae "problem", just a little more than we like. 

Ok, George. Not an algae "problem". What constitutes "a little more than 
you like"? Do you need to clean the glass every now and then?
> > My question is: does algae like more intensity or longer duration? 
> Difficult to answer.  My opinion is that algae is opportunistic; it
> will use what it can.  If the lights are on too long, the algae can 
> begin to use nutrients after the plants "go to sleep".   

I should experiment then with my current lights and see if reduced on 
time would curb algae growth.
> The exact amount of light is really dependent on a lot of things -
> types of plants, available nutrients, depth of tank, etc.  Do you have
> an algae problem now?  It's very "trial and error" to see what works
> for your situation.
Not an "algae problem" - just a little more than I like :-). Well, 
actually a lot more than I like. My tank is relatively new (12 days) and 
I already had what I thought was a red/brush algae attack (I think it was 
actually just green algae since when I boiled some sample in hot water, 
it did not turn red). A number of my plants, and the glass have green 
algae visible. I have six ottos  apparently busy cleaning away the 
green stuff, but I am not sure how effective they are. I also have two 
"false siamensis" who seem to be going after algae only occasionally. I 
thought they were the real thing when I found them among a tankful of 
flying foxes in a local store, but when I took them home, I compared them 
to Liisa's drawings and their stripe did not go all the way to their 
tail. All well, I thought 2 for $5.00 was too good to be true.

Oh yes, I have a 48x18x24 tank and 75% of the tank is planted mainly with 
Hygrophila polysperma, Hygro. corymbosa, Hygro. difformis, Rotala 
rotundifolia and macrandra, Cardamine lyrata, Vallisneria gigantea, 
some Cabomba caroliniana, a few Bacopa, various Echnodorus including three 
large bleheri, and some foreground Acorus like stuff I can't identify. 
All plants except the giant val and the foreground grass-like plants are 
doing well. The giant vals are all turning yellow and falling apart, and 
the little "grass" plants are yet to recover from the initial bleach 
treatment. One thing I notice is that all my stem plants have a lot of 
roots growing at seemingly every branch - hopefully it's a good sign...

 John Y. Ching (jyching at watnow_uwaterloo.ca)    |
 Pattern Analysis and Machine Intelligence Lab	| 
 Department of Systems Design Engineering      	| 
 University of Waterloo, Canada            	|