Methods: algae control or growing plants?

[Tom Barr]

Since GSA grows mostly on glass, rarely on plants, it would be more accurate I would think to assume it was a mix of CO2 and PO4 that prevents new germination of the GSA spores.

Competition has nothing to do with it.
This is rather obvious in terms of PO4, NO3 etc..........or light..........but............not CO2 very often.
Light and nutrients are easy to simply add excess non limiting resources.........this is a control for resource competition.

Many aquarist seem to have poor abilities to do the basics of competition studies for aquatic plants, but this is VERY basic logic in plant ecology and applies to algae as well.
We can verify the light and nutrients easily.

CO2 is much moire troublesome for most planted hobbyist.
Much harder to really verify, but..........you have 2 of the 3 main things, so take care of those, then focus on CO2 thereafter.
Use algae and good plant health as the test kit to slowly add more CO2.

CO2 is the most limiting nutrient for plants, and virtually never limiting for algae.
So it is really about hurting your plants and their growth, not algae, they just respond to poor plant health when there are plants present.
Nutrients/light otherwise when there are no plants.

Regards,
Tom Barr

[Tug]

Just looking at this myself and I'm finding non-limiting, PO4 stability helps. Say PO4 stability was the sign of a balanced something else, CO2. That might keep the algae from reacting. Drops or swings might suggest a distressed environment to some algae (GSA) and crap, it's just what their into. I get some I clean off, once a month generally. I run a yeast CO2 generator, so CO2 is likely involved. Anyway, when is it not?

I can't read my PO4, my test is in the trash can.
But, I dose ~7ppm/week+high amounts of PO4 from their food, etc.
Really, I don't spend a lot of time cleaning glass.

[Tug]

I see more GSA trying to limit (lower my EI dose after testing something) phosphate.

[darkoon]

thanks for the replies. I will try to increase PO4 level to >5 first, if that doesn't work, I will try to slowly increase CO2.
btw, the gsa i got in my tank grows on the old leaves of the plants too. now, could that have anything to do with excessive ambient light I have in the living room? my living room is lit up 7ish in the morning, and lights out 10ish at night. the tank lights on at 11, off at 7pm.

[Yo-han]

Read this thread with great interest. Always wondered why PO4 limitation worked for some people while others had no algae with high PO4.

But this whole story raises a new question: If everything is non limiting (nutrients, CO2) and you only use light to limit growth, than for algae there is a non limiting environment as well. Than what is limiting algae growth? It isn't CO2 or nutrients and in a normal tank there would be enough light for algae to grow.

So the only thing I could came up with is that plants leach some kind of hormone or chemical into the water that inhibit algae from growing. If so, why don't they sell this in a bottle? If not, how is it possible that algae don't grow in a non limiting environment?

Regards,
Johan

[Tom Barr]

Read this thread with great interest. Always wondered why PO4 limitation worked for some people while others had no algae with high PO4.

Simple, PO4 limitation can become stronger than CO2 limitation when you add say 15-30ppm of CO2 and then try to keep about 0.1-0.2ppm of PO4.
If you add 4 ppm of PO4, then the CO2 demand is more limiting.

This is the very basic tenent regarding Liebig's law of the limitation.

Since many did not realize that CO2 is also a limiting factor, and it's very poorly measured as well........they assumed it was limiting PO4 that was the key.
I falsified this hypothesis along with Steve Dixon.

So it CANNOT be due solely to PO4 "excess"(let's say 5ppm of PO4).
There has to be some other factor, it cannot possibly be PO4 independent of other factors.

There is simply no way that can possibly be true.

It does not say why other folks have algae etc.......only what it cannot be due to.
Other folks can replicate this and add good CO2, lower light etc.......and have no issues with algae.

But this whole story raises a new question: If everything is non limiting (nutrients, CO2) and you only use light to limit growth, than for algae there is a non limiting environment as well.

Why do you assume that algae that has a very very different life cycle in our aquariums is anything remotely like clonally reproduced plants?
There is no aquarium with a tank full of plants that is limiting to algae, this also goes for CO2 as well.
Many species of algae can grow at even less PAR light than most plants.

"What causes the algae spores to germinate or move from one life historty stage to the other?" is a much better question.

There are signals, not absolute concentrations that tell a specific alga when it a good time to germinate.
Maybe it's just variation in CO2, or O2, perhaps some bacteria in the root zone or NH4 spike, or a clogged filter, a drop off or reduced water flow, soem singal that the plants are now doing poorly and it's a good time to grow and complete their life cycle.

Plants? They just grow, we do not flower and raise them from seeds etc.

Than what is limiting algae growth? It isn't CO2 or nutrients and in a normal tank there would be enough light for algae to grow.

Seems they can tell when "someone else is there".
So can plants, they can tell the difference between a rock blocking their light and another plant or even their own leaves. Perhaps algae spores can detect a % of leaves or other algae absorbing certain wavelengths and reflecting mostly green light.
Since plants can tell if it's a leaf vs say a piece of wood, there's no reason why algae cannot as well.

I'm not aware of any real test done with respect to two groups, but it would be of interest.

So the only thing I could came up with is that plants leach some kind of hormone or chemical into the water that inhibit algae from growing. If so, why don't they sell this in a bottle? If not, how is it possible that algae don't grow in a non limiting environment?

Regards,
Johan

Many have loved this idea, and it does not work.
Many researchers have looked for allelopathic chemicals and it has never been shown in natural systems.
The controls and the test are very tough, it's not that the concepot etc is hard, but the controls have really caused some people to make bad conclusions and assumptions.

I think light and CO2 play larger factors with good reason, they are more pervasive and indicative of when someone else is there and in high enough biomass to cause problems. CO2 variation is good since it suggesta die off, or a change, or a lot of run off into a lake or stream. Same for light there as well.

Aquatic plants and algae compete mostly with respect to light, not much else.

[nipat]

Simple, PO4 limitation can become stronger than CO2 limitation when you add say 15-30ppm of CO2 and then try to keep about 0.1-0.2ppm of PO4.
If you add 4 ppm of PO4, then the CO2 demand is more limiting.---

I've been wondering about these for a while now but was afraid to ask.

From the sentences above, it can be interpreted that PO4 limiting doesn't cause algae but CO2 limiting does?

This baffles me. Because by your explanation about PMDD, I interpret that plants grow well even if CO2 is not optimum because they are PO4 limited. And when PO4 is added, algae grows because plants condition gets worse from CO2 limiting.

It sounds conflicting to me. Because how can plants be in better shape with PO4 limiting + not optimum CO2 (that is two limiting factors) than with PO4 non-limited at the same level of CO2 (only one limiting factor)?

And if so, then it sounds like we can be relaxed about CO2 level whenever PO4 is limited? And then isn't that an easier way to grow aquatic plants without algae and safer for critter too (from lower CO2 level)?

In my previous tank, I had 2 moments when it looked best. The first moment was when doing EI. Then I tore it down and restarted, this time I had to limit PO4 to control algae and that was the second moment when it looked best. Still don't know why.

[Tom Barr]

No, PO4 limits the plants and the CO2 limits the plants, the MOST limiting factor can shift from one to the other..........this is the Law of the Minimum that Liebig suggested and has since been made from a hypothesis, to a theory to a law of nature.
It's pretty hard core when it's a Law.

There is no conflict at all.

Aquarist might be confused because they are associating poor growth due to poor CO2 limitation to that of algae blooms.
These are two different issues.

Plant growth is where this all starts.
Plants have many ways to cope with PO4 limitation, they have far few ways to deal with large changes in CO2 concentration.

So the plants still grow okay with a moderate PO4 limitation, say reduced growth by say 20%.
If the PO4 is non limiting suddenly, then the CO2 limitation is more pronounced......more serious and much more detrimental to the overall metabolism of the plant.
This shuts everything down.

There are far more expensive enzymes associated with carbon metabolism than a decline in PO4.
The plants who can respond well to changes in CO2 are the weedy species, Egeria, Hydrilla, pondweeds, Vals and a few others.

Most species we keep cannot however.

So when the plants shut downs..........the algae appear.
If you strongly limit PO4, then you will get algae as well because that can shut a plant down as well if the limitation is strong enough, but CO2 metabolism is much more sensitive due to the amount of enzymes and the central role to all other functions.

PO4, ALL the plants have ways around this if the limitation is mild/moderate.

PMDD suggested moderate limitation, not strong limitation for PO4, many folks misread what Paul suggested.
He never once suggested absent or anything of the like for PO4, rather, 0.1ppm to maybe 0.2ppm.

If you look at this graph, which is an easier target to hit/add? At the B range or the D/C range?

Why bother with CO2 or PO4?
CO2 is only toxic if you lack O2, poor current etc, poor control/dosing of it, bad shoddy equipment, basically bad care with usage and/or way too much light for the demand it will create.

You should have a nice wide effective range that allows plenty of CO2 for plants without any STRESS for the fish.
If this is a narrow edge, then something else should be addressed, most likely O2/current etc..........cleaning the filters more often etc........too much light and what not.

Same for having to limit PO4.



Problem is with limiting PO4=> you get nasty GSA. It's not all peach and cream. Also, if you start with a general philosophy about what is best for management and fish health....you know it should start with light intensity, then progress to CO2.....and so on down the line....not start with PO4.
It works, but it is the tail wagging the dog and waste the light, the CO2 etc. It is also tougher to manage and test for than say light if you can get a PAR meter for a few minutes one time.

Anytime you have a limitation other than lighting, you are wasting light.
CO2, nutrients are very cheap relative to electrical energy.

[Tom Barr]

Oh, BTW Nipat, it was a good question!

[nipat]

Thanks Tom. It's clear now.