Maybe Tom has some new info on this since the post was back in 2001 I believe. This makes sense to a point, but my experiences with combatting algae do not quite mesh with this theory (unless my fish food fertilizing is creating a surplus of nutrients).
What do you think fish food adds that KNO3/KH2PO4 does not?
Hint, it's a species of nitrogen and is very deadly at higher levels.
-Duckweed kicks algae's butt by outcompeting them for excess nutrients, while my plants have still thrived.
The Duckweed is mainly out competing algae for light, not nutrients, that's secondary and then mainly for NH4. See above.
What happens when you add lots of plants as far as NH4 levels in a tank?
Up?
Or down?
Now repeat this with all sorts of species.
Now apply this to natural lakes, why is a nutrient rich lake chocked full of plants, while another lake with wind driven suspension pea soup?
How is my tank with 80ppm of NO3, 3ppm of PO4 algae free?
Note, this is a non CO2 tank.
If you claim that is causes something, then we should be able to add it and see some effect that you claim.
But.....we do not.
So we reject that hypothesis and move on to a better hypothesis that hopefully explains things better. I add NH4, I get algae consistently.
I add KNO3 and I never can induce algae to a stable system.
There might be other causes than NH4 also, NH4 cycles rapidly through a system and is hard to measure for professionals, let alone hobbyists.
-Extended light/high light have not made algae worse, in fact the opposite seams to be true (possibly due to plants growing better, beating out algae).
-Emergent plants seem to help as well.
So for the time being, I am not going to add any additional ferts to my heavily planted tank, because it seems to be in a good balance.
Higher light will work if you allow good biomass and established first, try it in the initial stages sometime:mad2:
Emergent plants mainly outcompete for light, which is why you saw what you saw, but concluded for the wrong reasons.
Note: you can also add other algae to "out compete" algae for NH4 also and many species will dominate once their biomass is rather high and you can see some species fade away in the process.
So what driving factor/s might be responsible over such a wide range or plant species and algae species and methods?
Light is one, it drives growth and CO2 uptake/nutrient uptake rates.
CO2 stability is another.
Stable nutrients is the last.
What universal parameter would be a good one to detect if it would be a good time to grow and that no one else is there and actively growing already?
NH4.
If the plants are limited, stunted, not enough biomass etc, then there will be a back up in the NH4 uptake.
If you have high light in conjunction with NH4, lower plant biomass etc you are asking for an algae bloom. Changing the CO2 all over will vary the NH4 uptake.
If you honestly believe in your theory, try trimming all those plants back and put say 20% of the biomass back. You'll get algae with the higher light you say you now have. It will not be due to excess nutrients either, it'll be due to NH4. You'll have 5x less uptake of NH4.
You can test PO4/NO3 before the trim and it can be near zero, and then later, you can add PO4 remover and NO3 remover(but not NH4 remover) to account for those.
After the plants grow back in, or if you add them back again, the algae will abate.
You can also add rotting plant trimmings and it can act much like excess fish food.
Regards,
Tom Barr