EI Theory question

[rharlow]

Trying to understand the theory and have a question that I can't seem to find the answer to. In regards to dosing, it is my understanding that we are dosing to maintain a sufficient level of nutrients such that there is no factor limiting plant growth. I'm confused in that, if there are sufficient nutrients, how come algae isn't growing. Yes the plants are growing, but we are dosing to keep levels up so why can't algae grow? And why does it seem that if we are out of balance does algae then start to grow, but not when all nutrients are available??

Chip

 

[VaughnH]

Algae start growing when they receive certain chemical signals telling them it is a good time to start a growth cycle. A tank full of healthy, growing plants will prevent the small ammonia surges that are one of the signals algae look for. Consistent CO2 concentration in the water during all lights-on periods will eliminate the fluctuating CO2 level that is another signal to the algae. As far as nutrients go, algae always have plenty to eat, but can't always be assured of access to light for long enough to go through a growth cycle. That is the major problem algae faces.

 

[rharlow]

I'm not sure this makes sense. So if I remove any ammonia spikes, algae won't grow? With lights on a timer, I'm sure that there are people who have had outbreaks in algae, so that would eliminate lighting as a source for the outbreak. Wouldn't CO2 fluctuate at night and there by signal algae to begin a growth cycle? Still confused.

Chip

 

[Tom Barr]

Well, algae are not limited in their rates of growth , except with light.
Plants?
Nutrients and CO2.

The algae have extremely small CO2 requirements, roughly, 100-10000 x less.
Adding CO2 can help algae grow faster also.

While not adding it does slow algae, typically folks without CO2..........also do not have high powered lights as well.

NH4 and CO2 uptake in plants is highly linked/coupled.

So if you suddenly stop adding CO2, or it goes all over, the NH4 uptake will also.

Measuring small transient amounts of NH4 is tough.
Also, higher light will increase the odds of getting an algae response with NH4 dosing.

So you have several things occuring at the same time, but most of it is CO2/NH4 related.

"Why algae do not grow" should not be your question though.
Rather: how can grow nice plants that are healthy and happy, that's the hobby we enjoy, not algae limitation and killing it etc.

We still need to deal with it etc, but the goal is really focusing on good non limiting nutrients, CO2 etc for the plants.

That is where folks need to place their energy, not trying to outwit algae.
Unfortunately, folks spend way too much time fretting over nutrients, and not enough about having less light and good CO2.

Less light= less demand.
That means you have less trouble and variation in the CO2 ppm content in your tank.

And when something goes wrong, it is not nearly as bad as high light.
Still, folks think if they get CO2, they must get high light, then they have all sorts of headaches and wonder why

So CO2+ lower light, say 1.5-2w/gal of T5's, a decent substrate, like ADA's AS, good current in the tank, lots of algae eaters, good frequent water changes etc, that is easy to deal with and produces nice results.

More light is not better, it's just more work and trouble.

This is a 1.5 w/gal ADA tank as an example:

Regards,
Tom Barr

 

[rharlow]

I think I understand!! So NH4 is the real culprit when it comes to algae? Unstable CO2 creates mini spikes in NH4? High light gives little room for error. Agree with primary concern should be with plants, just trying to understand the cycle. Regarding less light and good CO2 - is that basically plant related meaning it is dictated by what plants you intend to grow? I have a 65gal with 4 39W T5s with individual reflectors using three 6000K and one 6500K. My thoughts are that I could possibly reduce but my Rotalla wallichii tends to close up when one set is off. So would this mean that if I want to grow wallichii, then I need this higher level of light? Thanks Vaughn and Tom

Chip

 

[VaughnH]

CO2 and ammonia are not directly related. Fish produce waste matter, which contains ammonia. Rotting food, plant matter, dead fish, etc. also produce ammonia. None produce much, but enough for algae spores to detect. CO2, on the other hand, is largely introduced to the water externally, almost entirely externally in an aquarium. Variations in concentration of CO2 in the water, in nature, signal that something is changing - seasonal changes, for example. But, algae spores apparently can pick up those changes too. All of this is survival tactics for algae, "learned" by selective survival in larger numbers by algae that are good at picking the best times to bloom, thus producing the most "offspring". And, all of this "learning" took place long before any of us began the aquarium hobby.