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Re: Too much light?

> Hi everyone,
> I have a 24x12x16" tank with 2 x 20W lights and the tops of the plants were
> turning a red/brown colour. I removed one of the lights and they have
> recovered and are nice and green again. I had no co2 injection, kh of 4 and a
> high ph. There is a soil substrate covered with river gravel.

Ahhhh, no CO2 and a fair amount of light?
> I have since been lowering the ph. Can one have to much light? What is likely
> to be happening? I am assuming i must be low in co2.

Yes but how are you lowering the pH? Do not use anything to do this EXCEPT
CO2 gas. Read line that over a few times. Perhaps tattoo it on one's arm to
remember if needed:)
With a small tank like yours, adding DIY yeast CO2 would be quite simple.
But did you get any algae form the higher lighting?
By not adding CO2 your pH will go up for a few different reasons, not just
removal of CO2(a weak acid that will lower pH) but as a by product of NO3
uptake you also produce a OH- ion for each NO3 uptake as well. If you have
little current in your tank as well the areas around your plant's leaves
will really get quite high in pH compared to your actual readings or the
water. Then you have some plants and most algae that will split the HCO3 ion
and that will give you a CO2 and an OH- ion again raising your pH in 3
different ways.

 One removes the acid(pH goes up), two add OH-'s(again pH goes up for each).
You can stop this cycle easily and allow your plants to grow much faster,
healthier etc by adding CO2.

But if your not wishing to add CO2 yes, just leaving the light at 20 watts
should be fine. More light will grow plants faster and use up more CO2,
nutrients etc. You might not want this though. You may want slower growth
that's nice and healthy but slower. You'll have less plant choice but you
have more than many think and you can come up with a number of nice plants
and arrangements to keep you quite busy for many years:)
Don't use pH adjusters here either. Use a floating plant etc if you need
more nutrient removal etc. They (floating plants) don't have any CO2 issues.
Tom Barr 

> Thanks this is a great group.
> mick