Algae and Iron

4592 Views 37 Replies 8 Participants Last post by hoppycalif, May 13, 2020

hoppycalif

Discussion Starter · Jan 22, 2020

Diana Walstad, in her book, "Ecology of the Planted Aquarium", proposes that algae is limited in its growth by the limited availability of iron in the water. She says that while plants can get iron from the substrate, through their roots, algae doesn't have that ability, and has to depend on the iron in the water. Furthermore, that iron in the water has to be bio-available, in the form of soluble ions, Fe2+ and Fe3+. But, those ions have a very brief "life" in water because it easily bonds to various water soluble organic carbon compounds. As a result, algae has a difficult time reproducing unless there is a reliable source of Fe2+ and/or Fe3+ in the water.

One way those iron ions can be reliably available is if the iron that is bound to soluble organic carbon compounds is exposed to lots of light. When that bound iron is exposed to light of adequate intensity and spectrum, the light can cause the iron ions to be released into the water, by a process called photo reduction.

I find this extremely interesting, and one of the most compelling arguments about "why does algae take over my aquarium"? So, I am going to do a simple experiment to try to demonstrate that process.

I have a 10 gallon tank, modified with a divider into two adjacent 5 gallon tanks. The same light fixture lights both halves of the tank. See https://www.aquaticplantcentral.com/forumapc/diy-aquarium-projects/143379-tank-divider.html

If I dose each 5 gallon half of the tank with the same amount of iron (from Flourish Iron), but add the iron as the light comes on for one half, and after the light goes off for the other half, there should be a significant difference in availability of Fe2+/Fe3+ in the two half tanks. I should see more algae growth in the half with the most available iron.

I'm about 2 weeks or so from being ready to start my experiment.

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hoppycalif

Discussion Starter · #21 · Mar 7, 2020

My experimenting is hitting a snag! Before you can do a comparative test you have to be able to keep the two tanks growing equally, when they are set up equally. I haven't yet been able to do this. One tank is doing better than the other. And, neither is doing as well as I want. So, I'm thinking about adding/changing some plants. One thing I'm learning is that having floating plants, at least when they are Salvinia minima, it takes a lot of attention to keep those plants from blocking all of the light. They grow very fast! I have removed all of it, except what is contained in small plastic rings. But, even with that I need to remove excess plants weekly. I wish I had some hygro polysperma, but it is illegal to ship into California. I'm watching for someone selling it locally.

barongan

· #22 · Mar 8, 2020

interesting thread

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Yorkie

· #23 · Mar 18, 2020

Hi hoppycalif

What happened next? Please don't leave me in suspense!

Yorkie

Reactions: 1

hoppycalif

Discussion Starter · #24 · Mar 18, 2020

Progress: I found a source for hygro polysperma, and bought a few sprigs. Now each of the 5 gallon compartments has one. So, I'm still waiting until I feel like I could detect a change if I try any type of experiment. The Betta's are enjoying their homes, so that part is ok.

Reactions: 1

Yorkie

· #25 · Mar 23, 2020

That's great, Hoppy. I'm watching this with interest. You and I have something in common - we both share a love for running scientific experiments. Having a background in the physical sciences, I need to get my 'fix'.

Am I right in thinking that you have done a good many measurements on aquarium lighting? Your name is carved in my memory banks from a few years ago.

Yorkie

hoppycalif

Discussion Starter · #26 · Mar 24, 2020

Yorkie said:
That's great, Hoppy. I'm watching this with interest. You and I have something in common - we both share a love for running scientific experiments. Having a background in the physical sciences, I need to get my 'fix'.

Am I right in thinking that you have done a good many measurements on aquarium lighting? Your name is carved in my memory banks from a few years ago.

Yorkie

Yes, you are remembering right. I spend several years trying to find ways to determine how much light we have and how much we should have. It is still a mostly a guesswork subject.

When I got back to this hobby about 25 years ago, after I retired, I did it largely because there was so much to learn, and so much that was unknown about the hobby. I have never regretted that decision.

Yorkie

· #27 · Mar 27, 2020

hoppycalif said:
Yes, you are remembering right. I spend several years trying to find ways to determine how much light we have and how much we should have. It is still a mostly a guesswork subject.

When I got back to this hobby about 25 years ago, after I retired, I did it largely because there was so much to learn, and so much that was unknown about the hobby. I have never regretted that decision.

Hi Hoppy,

Thanks for your reply.

I also have a particular interest in aquarium lighting. There seem to be very few lighting manufacturers who design their products with the needs of plants in mind. And they blast aquarists' tanks with loads of photons at wavelengths that plants cannot use but algae and cyanobacteria bask in this light. But, I do realize that we want our plants to look right - not a weird shade of pink! This is not horticultural lighting.

JPC

hoppycalif

Discussion Starter · #28 · Mar 27, 2020

Yorkie said:
Hi Hoppy,

Thanks for your reply.

I also have a particular interest in aquarium lighting. There seem to be very few lighting manufacturers who design their products with the needs of plants in mind. And they blast aquarists' tanks with loads of photons at wavelengths that plants cannot use but algae and cyanobacteria bask in this light. But, I do realize that we want our plants to look right - not a weird shade of pink! This is not horticultural lighting.

JPC

I think the biggest lack of information we now have is algae and why it grows or doesn't grow. Diana Walstad's book is, in my opinion, on the right track in saying that it is the nutrients in the water that are the key to having algae or not having it. Algae have no access to the nutrients in the substrate, except for what leaches out into the water. And, I'm intrigued by the idea that it could be iron in the water that is the magic key to algae problems. Unfortunately, it is also very hard to find a good experiment that could enforce that idea.

Yorkie

· #29 · Mar 29, 2020

hoppycalif said:
I think the biggest lack of information we now have is algae and why it grows or doesn't grow. Diana Walstad's book is, in my opinion, on the right track in saying that it is the nutrients in the water that are the key to having algae or not having it. Algae have no access to the nutrients in the substrate, except for what leaches out into the water. And, I'm intrigued by the idea that it could be iron in the water that is the magic key to algae problems. Unfortunately, it is also very hard to find a good experiment that could enforce that idea.

Hi Hoppy,

Diana Walstad, in her book, talks about light wavelengths below 520 nm promoting algae growth. But, plants also need light from this part of the spectrum. Chlorophyll a and b peak responses occur at 430 nm and 453 nm, respectively. However, with a lighting fixture that permits control over its spectrum, the amount of light being emitted below 520 nm can be reduced. The fact that white LEDs are essentially blue LEDs with the appropriate phosphor added results in a lot of light from 400 nm - 520 nm, as I'm sure you are aware. Please see the attached.

Yorkie

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hoppycalif

Discussion Starter · #30 · Mar 30, 2020

Yorkie said:
Hi Hoppy,

Diana Walstad, in her book, talks about light wavelengths below 520 nm promoting algae growth. But, plants also need light from this part of the spectrum. Chlorophyll a and b peak responses occur at 430 nm and 453 nm, respectively. However, with a lighting fixture that permits control over its spectrum, the amount of light being emitted below 520 nm can be reduced. The fact that white LEDs are essentially blue LEDs with the appropriate phosphor added results in a lot of light from 400 nm - 520 nm, as I'm sure you are aware. Please see the attached.

Yorkie

Yes, I have seen those charts, but I haven't seen any data that would support a belief that certain wavelengths of light cause algae problems. That, too, is a very hard experiment to try.

mistergreen

· #31 · Mar 30, 2020

Besides, limiting your aquarium lights to a certain spectrum to avoid algae wouldn't look aesthetically good.

Yorkie

· #32 · Apr 5, 2020

hoppycalif said:
Yes, I have seen those charts, but I haven't seen any data that would support a belief that certain wavelengths of light cause algae problems. That, too, is a very hard experiment to try.

Hi Hoppy,

Perhaps I've confused things by referring to the chlorophyll a and b peaks. I wasn't suggesting that specific wavelengths could promote growth of algae. Diana Walstad has drawn that to our attention by introducing us to iron photoreduction at less than 520nm.

Now, I do want to suggest that certain wavelengths may indeed promote algae (and BGA). Please see the attached absorption spectra. The two accessory pigments, phycoerythrin and phycocyanin are to be found in BBA and BGA, respectively. So, light in the band from 500nm to 620nm may have the potential to promote both BBA and BGA. And, higher plants only require a small proportion of light in this band. I may have suggested elsewhere on this forum that reducing the intensity of light in this mid-band when the tank is not 'on display' may help to reduce BBA and BGA. Then, when the tank is 'on display' for the benefit of we humans, the spectrum would switch to one that is aesthetically pleasing.

Yorkie

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hoppycalif

Discussion Starter · #33 · Apr 6, 2020

There is certainly some information that might indicate that the spectrum of the light we use could affect how much algae we have. But, we would need to experiment to determine if it really does that, and that would be difficult to do. Changing the spectrum, while maintaining the same light intensity isn't an easy thing to do.

crinum1111

· #34 · Apr 25, 2020 (Edited)

Hi,
Recently read the Walstad book I found it helpful too and this was a key point of interest for me as well. My interpretation after a few readings was to deliver iron to the roots .With some caution though as iron toxicity in low ph substrate is of potential concern . Don't know if even high cec rated substrates take up the iron aggressively enough . I might try dosing moderately with full spectrum ferts ,plus bit of extra npk ( i'm running no fish currently ), a bit of trace and flourish tabs on fast growing iron hungry plants .If I get a good crop of fast growing iron hungry plants going probably switch back to just full spectrum fertilizer then .

hoppycalif

Discussion Starter · #35 · Apr 25, 2020

My experiment isn't going to be a success. I suspect I don't have enough substrate in it, and the plants are not doing very well as a result. But, if I can't get both sides of the tank to start out doing well it isn't possible to see the effect of changing something on just one side. When I think about this some more I will probably start over again, but I need to keep the two betta's living while I do it. I'm still intrigued by what I read in Diana's book about iron.

Yorkie

· #36 · May 1, 2020

hoppycalif said:
My experiment isn't going to be a success. I suspect I don't have enough substrate in it, and the plants are not doing very well as a result. But, if I can't get both sides of the tank to start out doing well it isn't possible to see the effect of changing something on just one side. When I think about this some more I will probably start over again, but I need to keep the two betta's living while I do it. I'm still intrigued by what I read in Diana's book about iron.

Hi hoppycalif,

It's a shame that the plants are not growing well and that your experiment will not be a success. I will follow this with interest should you decide to try again.

Yorkie

hoppycalif

Discussion Starter · #37 · May 1, 2020

I have torn down the tank(s), and have replaced the substrate so it is almost a full 2 inches total thickness, with "dirt" (Black Gold from Ace Hardware) making up the bottom 3/4-1 inch. The top is Safe T Sorb. I should have more plants arriving on Monday, and I salvaged several from those still living. I plan to not use the little in-tank filters again, since the Bettas don't really like them.
By next Wednesday or so I should have it back to life. Meanwhile the two Bettas are in big cylindrical vases, in about a pint of water. My fingers are crossed!

hoppycalif

Discussion Starter · #38 · May 13, 2020

I have my double 5 gallon tank set up again, almost. I will add some more crypts as soon as I get them, probably in 2 days. The substrate is much better now, but I am still poking it every couple of days and getting lots of bubbles. So far, no bad smell, so the bubbles aren't that bad. Now, I will see if I can treat both halves the same and get two equally good/bad tanks.

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