http://www.bio-web.dk/op/pdf/TAG_2002_15_7.pdf

I have long rejected this hypothesis that allelopathy plays a significant role in aquariums in regards to plants and algae.

Many seem to still think it's likely.
But few experts will say that it is, I've proposed numerous experiments one might do to show this for themselves.

The above article was in TAG several years ago and we(mostly myself) pretty much beat the idea into the ground.

Ole will be at this years' AGA event BTW.
I have some questions for him too:-)

Regards,
Tom Barr

I'll grant it some possibilities, but I'd expect nutrient potential to become a more likely factor ! By the time Allelopathy comes into play aren't you already leading with your chin ? In laymens terms don't we already have enough sound reasoning to Water Change the Bloody Tank ??? LOL. If Allelopathy were to become a dominant factor in aquariums You're just not paying attention...

What about a non CO2 plant tank though?
E.g. no water changes for months/years?

You can still remove the chemicals with Activated carbon in such tanks also :idea:

By default, the non CO2 approach does not test the water parameters seldom if ever. That's part of the allure and simplicity.

What I did some years ago, was this:

Observation: some plants did poor in the the non CO2 tank. Some did well.
Over time things ebbed and flowed, some plants wasted, some flourished.

I removed the soil and dosed just inorganic ferts with plain sand/flourite.
I found that fish food left you a deficit of K+, Ca, Mg, SO4(likely), often times NO3 and PO4. Traces are often added to non CO2 tanks so those where not tested nor would doing so reveal any new insight due to testing issues for Fe.

Fish waste added a fair amount of N and P, but often once the plants grew in, these where very low and consumed rapidly by hungery plants.

Adding KNO3 and KH2PO4 enhanced growth.

Not all aquarist have the same fish loads either.
Adding trhe GH booster really helped things, once a week of these was enough to allow you to grow most plants, up from 50 species to about 200 with these routines.

With the test kits, I found a fairly robust range that was about 7-12 x slower than the CO2 enriched 3-4w/gal tanks.

Most of the problems folks assoicate with plants in non CO2 tanks are not allelopathic, rather, limitation based.

You can be an arm chair philosopher and speculate till the cows come home, offer research support etc, but unless you test and see if something works or not, you will not gain much new insight.

From such test and questions, we learn a lot more than from speculation.
We often specyulate to hopefully answer the question/s in the future and have some one new come along and advance what is known about a subject.

Raising good questions is also a great idea.
She certainly did this more than any other IMO.

Regards,
Tom Barr

I run 3 main tanks these days. You may be the root cause of this long term experiment ??? At the very least the catalyst !

1 High Tech (No holds barred, on the lunatic fringe, Heavy on the LUNATIC)
1 low tech (Yeast reactor Co2 , DIY reactor, Strict EI and maintenance)
1 No Tech (Classic Dutch: Don't touch it you'll break it ! )

In the long term this may allow me some reasonable data ? But they all exhist to beg the question

All other tanks are incidental, or experimental, but those 3 main systems are my litmus test.

I don't believe there is a perfect method...but There Is something for everyone. Life as I know it seldom recognizes absolutes. This is an inherrent risk of corroborating research.

One of the greatest strengths of a diverse forum is in it's numbers ! This alone allows us all to test the limits daily. A group of like minded individuals that ask the very same questions without end. While it may appear tedious it is in fact honing, and keening the hobby, and the science. Prof M

There is no perfect method because each has a trade off, which method best suits the goal of the tank/it's owner etc is the primary focus for myself.

Regards,
Tom Barr

I always felt that competition for resources was not the only reson plants seem to have a bad effect on algae grows.
I noticed that a "happy plant" won't be attacked by algae even in an aquarium with very few plant. while in the same aquarium, a "sad plant" can be attacked.

So maybe what I call "happy plant" is a plant strong enough to fight algae with allelopathy.

That's cool

So define a sad vs a happy plant more specifically.
What might be the issue there?

You need to provide similar conditions and acclimating time for the plant comparison also.

Sad plants often are stunted and take a long time to recover. Sad plants often do not have good growing conditions to begin with for that plant, some plants, say Hydrilla or Milfoil are very strong competitiors.

In a tank with very few plants, I'll assume such a tank si non CO2, generally a fish tank with some plants added?

In such cases the sad plant gets beaten out for nutrients.
Thus the sad plant is beaten out for nutrients.
Then it's only a substrate for algaer growth like a rock or the glass etc.

The healthy plant is able to out pace formation of the algae, even Anubias are able to do this.

Regards,
Tom Barr

OK, so maybe it's not allelopathy, but the "out pace formation" (That was one of my theories but I never heard about it until now).

I just never understood the "competition for resources" theory, because in a high-tech tank there is always enough nutrients but still no algae.

I hear people advising to plant very dense in a new aquarium, is this at all true?

How can we distinguish between the two factors - "allelopathy" or "out pacing of formation"?
Perhaps taking a very big tank, with only one plant and lots of nutrients and CO2 (very low concentration of toxic),
and compare it with a tank with the same conditions but many plants (of the same kind).

Well, one is growth rate and light competition, if anything, plants outcompete algae for that resource, CO2, and NH4.

Not NO3, PO4, Fe etc.
Plants cannot outcompete the algae effectively for that, periphyton studies have long shown that with respect to PO4 in wetalnds, about 250% lower PO4 levels than submersed macrophytes can withstand.
And it was a very good studies on tropical conditions and plants.

Very applicable to this situation.

also, plants reproduce vegeatively in our case, algae are all sexual, thus they produce spores to respond to different parameters. What germinates a spore to bloom?

That is different than a stable system where two adult species of plant and alga are present.

Many try to compare these two together as equals, when this is like comparing aquatic plant seeds and algae spores in competive fashion.

It's not the same.


Regards,
Tom Barr

I'm a little lost...
What is the main reason algae do not thrive in a high-tech tanks (planty of light, co2, nutrients...)?