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Light Compensation Point and optimal PAR levels

dw1305 said:
Hi all,
I'll try and put together a "plant physiology primer" before the end of the summer. I have lots of powerpoints etc. so it will just be a case of cut, pasting and referencing the relevant bits.

If any-one does have questions about photosynthetic processes I point them towards SAPS http://www-saps.plantsci.cam.ac.uk/qanda_photo.htm, it is for schools but has lots of good stuff on it.

There is a brilliant powerpoint of photosynthesis here (by prof John Gray of Cambridge University here):
http://www-saps.plantsci.cam.ac.uk/summer/2005/edinburgh2.ppt. It is a thing of beauty as well as a great resource.

cheers Darrel
Click to expand...

Hey, I know Dr Lui, he's in the other lab here at Davis.
He does some cool research.

http://www.plantphysiol.org/cgi/content/full/136/4/3945

Uses GFP a lot for neat videos of movement inside live cells.
I just kill weeds, nothing this cool 😳

Regards,
Tom Barr
 
tyrophagus said:
I took some PAR readings today after my meter arrived and I have 40 at the surface dropping to 18 midwater then about 12 at substrate level.
I'll take some more readings when I can and perhaps produce a PAR chart for the LED lights.

How slowly should I increase the light intensity? I was thinking of about 3 PAR a day at the substrate until it reaches 30.
Click to expand...

30-40 is fine at the sediment, make sure it's fairly even all over the tank's sediment, +/- 10 or so PAR is fine.

12 is not much/enough for most situations.
So you do need more light.

This is rare me saying that 😀
But, this is why we have light meters to answer such questions.


Regards,
Tom Barr
 
ghostsword said:
High O2 while the CO2 is on.
Click to expand...

How does one achieve this? The water movement of a air pump will dissolve CO2 much faster, right?
Click to expand...

Good water movement/flow.
Do we stop caring for our fish in the quest for plants?

Rubbish.

I've long promoted doing good feeding/foods for fish, as well as frequent good sized water changes and good current, over filtered. I can fix algae, plant issues, they are nearly immortal, fish? They die if you look at them wrong.
I always error to the fish for this reason.

Good water changes/flow etc will keep the O2 high and stable. You also have good dense plant growth, this adds pure O2 while the CO2 is on if the plants are well cared for.
With lower light, you do not have a high CO2 demand either.
This will make management and easier and less risk for fish.

I use a simple rule, if the water is not breaking the surface but there a decent ripple, I'm good.
You do not want aeration, or bubbles entering from too much current at the surface ...that degasses too much.
This way the O2 is about 7-8ppm most of the 24 hour period and then goes to about 10-11ppm while the CO2 is on for 8-10 hours.

With good current, feeding well/frequently, good grade of food etc, clean water, lower light(lower CO2 demand)........this does fish very well.

KNO3 is added but kept at 25-30 ppm or less which is less than 7ppm N-NO3ppm. Not much really, but plenty for plants.
Since this is inorganic source, rather than from over feeding fish waste etc that starts off as organic N then to NH4......... KNO3 by passes that and also drains no O2 in the process(fish waste and bacterial conversion to NO3 takes 3 O's).

Regards,
Tom Barr
 
plantbrain said:
ghostsword said:
High O2 while the CO2 is on.
Click to expand...

How does one achieve this? The water movement of a air pump will dissolve CO2 much faster, right?
Click to expand...

Good water movement/flow.

Good water changes/flow etc will keep the O2 high and stable.

I use a simple rule, if the water is not breaking the surface but there a decent ripple, I'm good.
You do not want aeration, or bubbles entering from too much current at the surface ...that degasses too much.
This way the O2 is about 7-8ppm most of the 24 hour period and then goes to about 10-11ppm while the CO2 is on for 8-10 hours.

With good current, feeding well/frequently, good grade of food etc, clean water, lower light(lower CO2 demand)........this does fish very well.


Regards,
Tom Barr
Click to expand...

Ok, so I am on target then. I thought that to provide the O2 mentioned I had to start the air pump during day time.

Currently I have a water current from the filter outlet at just under water level, and the koralias also move the water, however the air pump only comes at night time, from 1200 to 0600, and the CO2 from 0600 till 2200, with all lights off at 2300.

Thanks for the brief explanation.
 
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