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Discussion Starter · #1 ·
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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Discussion Starter · #3 ·
I will have to measure the pH when I get closer to starting this. First I need to get a couple of Betta's to occupy the two tank halves. The water is pretty hard, but I forget the numbers right now.
 

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Discussion Starter · #5 ·
Interesting. Since the pH and water is the same in both tank halves, pH doesn't really matter. There's also no need for fish.

You will have plenty of other confounds and wiggle room in your reporting, so I would keep it simple and do it as a "pilot experiment." If you get a dramatic difference, then you can trumpet your results and we can enjoy hearing about the details and speculations.

If you get no effect, then I could point to not doing experiment in triplicate. Or that both tank halves were exposed to light at some point during each 24 hr cycle. In the published experiment, there was light in each case, but one set had normal light, the other light where all the shorter, more energetic wavelengths (below 520 nm), which create reduced, algae-stimulating iron, had been removed. Algae didn't grow with the shorter wavelengths, but it did with normal unrestricted light.
I agree that this will not prove anything, but I'm just looking to see if, in a normal planted aquarium setting, does big differences in how iron is dosed cause a big difference in algae problems. It has to be a big difference to mean anything at all for me because I find it very hard even with this set-up to get two tanks to act the same. So, the first step has to be finding out just how much variance is "normal". I have no idea what I will find out, other than that the odds are that I won't see any significant difference.

The reason for the two fish is to have something else to enjoy with this odd tank. I will really be embarrassed if one fish survives and the other gets sick.

I enjoy doing this kind of thing!:D
 

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Discussion Starter · #10 ·
I now have a Betta in each tank, looking healthy, and both tanks look the same, as far as the plants are concerned. The pH of the tank water is about 6.6-6.8, which I assume comes from the tannins released by the dirt substrate. My tap water has a higher pH.
 

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Discussion Starter · #13 ·
The plants iin the tanks are Sagittaria subulata and a hybred swordplant, plus floating Salvinia. I'm not interested in the effect on the plants, because it is well proven that iron helps the plants. My interest is the effect on algae, primarily on the effect vs the amount of light the iron fertilized water gets. I'm very interested in the idea that iron shortage can inhibit algae growth.
 

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Discussion Starter · #16 ·
My experiment is starting!! The two tanks are now pretty well established, with no obvious algae, almost exactly the same plants in each, same light, same substrate, and a Betta in each one. Tonight I will start dosing Flourish Iron, to get 0.10 ppm in the water in each tank, dosed after lights out at night, every other night. If all goes well, I will get no obvious algae. After about 2 or 3 weeks, I will change the dosing time for one tank to right after the light comes on.

Now I need a Swiss trolley to ride in so I can get a brainstorm going!!
 

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Discussion Starter · #18 ·
Dosing the iron, in low dosages, at night should cause all of it to be taken in by the plants, or attached to dissolved organic carbon in the water, leaving none for the algae. But, dosing iron as the light comes on may cause the iron attached to organic carbon to be released into the water as Fe ions, if photo reduction occurs with the level of light intensity we use. That would make it more available to algae, as well as to the plants. And, that might cause algae to start growing vigorously. I expect to see no algae response, because I expect that photo reduction is trivial at the level of light intensity we use. I wouldn't bother with this if I had never had an algae problem at low aquarium light levels. It would be very interesting if I do get an algae growth response. Meanwhile, I will be convincing myself that I can get two tanks to grow without algae problems, making additional testing possible.
 

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Discussion Starter · #20 ·
I don't think you are missing anything. It seems that nothing in an aquarium is a simple thing. I got interested in this when I read about the possibility that algae is handicapped by being able to get iron only from the water, but bioavailable iron in the water is rapidly removed. That made me wonder why algae is such a big problem in aquariums. The photo reduction idea might be a big factor. I will be astonished if I see a major difference with my little experiment, but I will be enjoying trying to do such an experiment, so it doesn't really matter.
 

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Discussion Starter · #21 ·
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.
 

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Discussion Starter · #24 ·
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.
 

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Discussion Starter · #26 ·
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.
 

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Discussion Starter · #28 ·
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.
 

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Discussion Starter · #30 ·
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.
 

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Discussion Starter · #33 ·
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.
 

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Discussion Starter · #35 ·
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.
 

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Discussion Starter · #37 ·
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!
 

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Discussion Starter · #38 ·
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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