How much silicates do diatoms need to grow.

[Randy Holmes-Farley]

Oh wow, well beyond what I was reading. I read. .01 to .04ish but 1.0 to 2.0..

Alright I need to really look into this. Thank you

Those may be enough, but where did you see them? I’ve not seen much hobby data on it.

 

[BuddyBonButt]

Those may be enough, but where did you see them? I’ve not seen much hobby data on it.

Can't even remember, I know It was somewhere on here. I think it was someone asking if their silica levels (it was in the range that I'm going for) would actually grow diatoms and people were back and forth on if it would or wouldn't. The original post was about figuring out if they had diatoms or dinos.

But I also can't find any info on it. I would love for a BRS investigates video on it honestly but I'm going to try around 0.03 and see what happens within the week. The bottle does say to increase by 10% every 2 weeks if you don't see results.

 

[Randy Holmes-Farley]

Can't even remember, I know It was somewhere on here. I think it was someone asking if their silica levels (it was in the range that I'm going for) would actually grow diatoms and people were back and forth on if it would or wouldn't. The original post was about figuring out if they had diatoms or dinos.

But I also can't find any info on it. I would love for a BRS investigates video on it honestly but I'm going to try around 0.03 and see what happens within the week. The bottle does say to increase by 10% every 2 weeks if you don't see results.

The levels I added drop to undetectable by test kit in only a few days, so I doubt the exact dose matters much.

 

[GarrettT]

It’s really doesn’t take much. I have plenty of diatoms and my SI is only 0.2ppm. I remember reading somewhere that copepods are much more responsive to the diatoms < 1ppm SI. I only say this because I see you have a mandarin.

 

[BuddyBonButt]

The levels I added drop to undetectable by test kit in only a few days, so I doubt the exact dose matters much.

Alright, well heres to hoping I don't see those dino demons anymore. I had amphidinium I think but a blackout worked so well so maybe prorocentrum? Although it originated from the sand which also goes back to amphidinium... idk, just thankful it's gone for the moment. Thanks for your input!

 

[Randy Holmes-Farley]

It’s really doesn’t take much. I have plenty of diatoms and my SI is only 0.2ppm. I remember reading somewhere that copepods are much more responsive to the diatoms < 1ppm SI. I only say this because I see you have a mandarin.

Just to be sure we are all talking the same units of measure, 1 ppm Si = 2.2 ppm SiO2

 

[GarrettT]

Just to be sure we are all talking the same units of measure, 1 ppm Si = 2.2 ppm SiO2

I use a Hanna Silica LR checker. I believe that the ppm tested is in fact SiO2, but could be wrong.

 

[Randy Holmes-Farley]

I use a Hanna Silica LR checker. I believe that the ppm tested is in fact SiO2, but could be wrong.

Bear in mind the number you see is after they have grown and taken it up. :)

 

[BuddyBonButt]

Here's a section from one of my articles:

With one exception (discussed below) all diatoms require silica for growth, and low silica levels cause significant changes in the cell cycle.7 Silicon is a major limiting nutrient for diatom growth in certain parts of the oceans,8 although iron,9 nitrogen, and phosphorus can also be limiting. There have been many studies on the uptake of silica by diatoms. Most diatoms take up silica in the form of silicic acid, although one has been shown to take up the silicate form.10 If absorbing silica is a limiting factor, then it makes sense to transport silicic acid since it is present at much higher concentrations than is silicate, and hence is potentially easier to transport.

Different diatom species have different abilities to absorb silica from the water. That is, as the silica concentration drops, some diatoms can continue to pull silica from the water while others cannot. Most diatoms have half maximal rates of silica absorption of 0.7-10 mM (0.04 – 0.6 ppm SiO2),2 but some are substantially higher, up to about 60 mM (2.6 ppm SiO2).2 The in-situ average for biogenic silica uptake in the surface layer of the equatorial pacific showed half maximal uptake at a silica concentration of 1.6 mM at 3°S and 2.4 mm at the equator, which was close to the silica concentrations present.3

There apparently are genes for many different silica transporters in each of the diatom species that has been investigated.8 Diatoms also somehow maintain internal silicic acid concentrations at levels higher than its solubility, but the mechanism for accomplishing this is unclear. Nevertheless, it is obvious that this facilitates the deposition process, and inhibits dissolution of the existing frustule. Diatoms apparently use proteins to guide the deposition process, where soluble silica is converted into the intricate solid frustule, but exactly how this role is accomplished is not known.8

In a reef tank like mine with silica concentrations below 0.8 mM (0.05 ppm SiO2, the practical limit of the Hach silica kit), some diatoms will have a hard time absorbing silica. Many reef tanks may, in fact, be selecting for diatoms that are able to get enough silica at the low concentrations typically available. Are diatoms silica-limited in reef tanks? That question is addressed experimentally below.

In the oceans, diatoms are silica limited in some natural settings (like the polar regions and the Sargasso Sea, where the ambient silica concentration is less than 1 mM (0.06 ppm SiO2).11 There have also been many cases where eutrophication of natural waters has raised nitrogen and phosphorus levels to the point where silica has become limiting,12 even when it was not limiting in pristine waters. In reef tanks, where nitrogen and phosphorus are often not in short supply, it makes sense that silica could be limiting. In case you were thinking that silica limitation to diatom growth is necessarily a good thing, there are drawbacks. The limitation of silica, inhibiting the growth of diatoms that would otherwise take up the limiting nutrients nitrogen and phosphorus, has even been implicated in blooms of cyanobacteria.

Hey @Randy Holmes-Farley can disturbing the sand from a tank that's 8 months old cause diatoms to start to appear? I recently started water changes (dinos) and I stirred sand a little on accident. Now I have a pistol shrimp and it's really going at the sand. I'm having crazy diatom growth and this happened when I got dinos and I'm concerned they might be coming back. I really don't want to spend another 4 months fighting them. A microscope confirms that they are in fact diatoms and it's a Rusty Brown coating. My tank went from short-lived diatoms to 4 months of dinos to 3 months of hair algae and now I'm having diatoms again. Am I in some kind of weird Loop?

 

[Randy Holmes-Farley]

Hey @Randy Holmes-Farley can disturbing the sand from a tank that's 8 months old cause diatoms to start to appear? I recently started water changes (dinos) and I stirred sand a little on accident. Now I have a pistol shrimp and it's really going at the sand. I'm having crazy diatom growth and this happened when I got dinos and I'm concerned they might be coming back. I really don't want to spend another 4 months fighting them. A microscope confirms that they are in fact diatoms and it's a Rusty Brown coating. My tank went from short-lived diatoms to 4 months of dinos to 3 months of hair algae and now I'm having diatoms again. Am I in some kind of weird Loop?

What type of sand? Unless it is silica sand, I wouldn't have expected diatoms to result from stirring sand.

It might be releasing nutrients that were down in the sand from degraded organics.

 

[BuddyBonButt]

What type of sand? Unless it is silica sand, I wouldn't have expected diatoms to result from stirring sand.

It might be releasing nutrients that were down in the sand from degraded organics.

Hey, thanks for the response. It's caribsea special grade. About 2.5 inches of sand.

I do have 2 conch, 3 Nas snails, and now a sandsifting star so plenty of sand movement. I have a 5 stage rodi with 2 chloramine carbon blocks and recently found a channel in my di resin allowing around 8tds through and towards the end when discovering the issue almost 14tds. I've since fixed that but I did 25 gallon water changes with that. Could that be the source? Just ride it through again as if it was cycling due to the di issue?

 

[Miami Reef]

Hi @Randy Holmes-Farley

Most diatoms take up silica in the form of silicic acid, although one has been shown to take up the silicate form.

Is there a way a person can dose silicic acid instead of sodium silicate?

 

[saltyhog]

Thanks for the reply.. since this post the bloom of whatever it is looks more like brown cyano perhaps? I don't recall cyano just blowing away off the rocks with a good turkey baste but the stuff in the sand is matty and is now looking more like cyano, although brown in color. If you would please, take a look at let me know your thoughts. Also, in small patches some areas look to be turning green.. I'm hoping this is a sign of it breaking down. Thanks again!

Those pictures really don't look like diatoms...looks much more like dinoflagellates. Do you have access to a microscope? That would be the best way to not only tell if they are dinos but which type they are.

 

[Randy Holmes-Farley]

Hi @Randy Holmes-Farley



Is there a way a person can dose silicic acid instead of sodium silicate?

The form present in seawater at a fixed pH will not matter if it is added as silicic acid or silicate. It equilibrates to a fixed percentage of silicic acid and silicate. Silicic acid is not especially stable to dehydrating to silica, SiO2. So it is unlikley to be a good dosing product.

Silica In Reef Aquariums

Why would I recommend dosing silica? Largely because creatures in our tanks use it, the concentrations in our tanks (at least in mine) are below natural levels, and the sponges, mollusks, and diatoms may not be getting enough to thrive.

reefs.com

from it:

Silica in the Ocean​

Dissolved silica in the ocean largely takes the form of silicic acid, Si(OH)4. Since it is acidic and has a pKa somewhat above normal seawater pH values (pKa ~ 9.5 in freshwater; possibly it is a bit lower in seawater), about 5% of it will be present as silicate, Si(OH)3O–. Apparently, many diatoms take up the Si(OH)4 form directly, although there is some evidence that certain organisms take up Si(OH)3O–. In this article, I will not generally refer to silicic acid or silicate unless I am specifying one or the other. Typically I will refer to the sum of them as “soluble silica” or just silica, if the context is clear.

 

[Miami Reef]

The form present in seawater at a fixed pH will not matter if it is added as silicic acid or silicate. It equilibrates to a fixed percentage of silicic acid and silicate. Silicic acid is not especially stable to dehydrating to silica, SiO2. So it is unlikley to be a good dosing product.

Silica In Reef Aquariums

Why would I recommend dosing silica? Largely because creatures in our tanks use it, the concentrations in our tanks (at least in mine) are below natural levels, and the sponges, mollusks, and diatoms may not be getting enough to thrive.

reefs.com

from it:

Silica in the Ocean​

Dissolved silica in the ocean largely takes the form of silicic acid, Si(OH)4. Since it is acidic and has a pKa somewhat above normal seawater pH values (pKa ~ 9.5 in freshwater; possibly it is a bit lower in seawater), about 5% of it will be present as silicate, Si(OH)3O–. Apparently, many diatoms take up the Si(OH)4 form directly, although there is some evidence that certain organisms take up Si(OH)3O–. In this article, I will not generally refer to silicic acid or silicate unless I am specifying one or the other. Typically I will refer to the sum of them as “soluble silica” or just silica, if the context is clear.

That reminds me of ammonia and ammonium. Dosing pure ammonia is expensive and difficult, but dosing ammonium will change forms between both depending on pH.

 

[Randy Holmes-Farley]

That reminds me of ammonia and ammonium. Dosing pure ammonia is expensive and difficult, but dosing ammonium will change forms between both depending on pH.

Yes, exactly the same effect. Same too for bicarbonate and carbonate. Only the final pH determines the ratio in the water. :)

 

[Miami Reef]

Yes, exactly the same effect. Same too for bicarbonate and carbonate. Only the final pH determines the ratio in the water. :)

Is there more carbonate or bicarbonate in a higher pH?

Edit: I think carbonate will be more abundant at a higher pH?

 

[Randy Holmes-Farley]

Is there more carbonate or bicarbonate in a higher pH?

Edit: I think carbonate will be more abundant at a higher pH?

Yes. There's a nice graph here:

https://www.nature.com/scitable/content/ne0000/ne0000/ne0000/ne0000/25853439/2-626w_1_2.jpg

 

[Miami Reef]

Yes. There's a nice graph here:

https://www.nature.com/scitable/content/ne0000/ne0000/ne0000/ne0000/25853439/2-626w_1_2.jpg

Thank you.

Last question. :)

What’s the affinity of silica to GFO? If someone is trying to just slightly lower their phosphates, but they do want silica in the water. Does GFO prefer silica over phosphates? Will too much silica exhaust GFO before the phosphates get lowered?

 

[Randy Holmes-Farley]

Thank you.

Last question. :)

What’s the affinity of silica to GFO? If someone is trying to just slightly lower their phosphates, but they do want silica in the water. Does GFO prefer silica over phosphates? Will too much silica exhaust GFO before the phosphates get lowered?

I do not know the relative affinity with high accuracy. Both are bound to a significant extent. I think that phosphate is more strongly bound, based on related data such as that below where phosphate is better able to prevent binding of a third ion (arsenate) than is silicate. hence I think sufficient phosphate will displace silicate on the GFO.

Impact of phosphate, silicate and natural organic matter on the size of Fe(III) precipitates and arsenate co-precipitation efficiency in calcium containing water

Removal of arsenic (As) from water by co-precipitation with Fe(III) (oxyhydr)oxides is a widely used technique in water treatment. Nevertheless, As re…

www.sciencedirect.com

From these results it can be concluded that the removal of As(V) in the presence of Si and P was affected mainly because of the reduced adsorption of As(V), whereas in the presence of NOM a reduced adsorption and a reduced Fe(III) removal both were responsible. Phosphate reduced As(V) adsorption the most, mainly because of its similar affinity for adsorption sites and higher concentration than As(V). But, the overall As(V) removal efficiency was reduced the most with the variations in NOM concentrations, mainly because NOM rendered a large portion of Fe(III) mobile in the solution.