some interesting reading about diatoms.

[boxfishpooalot]

Quote "The use of silicon by diatoms is believed by many researchers to be the key to their ecological success. In a now classic study, Egge & Aksnes (1992) found that diatom dominance of mesocosm communities was directly related to the availability of silicate. Above concentrations of silicon of 2 mmol m-3, diatoms typically comprised more than 70% of the phytoplankton community. Raven (1983) noted that, relative to organic cell walls, silica frustules require less energy to synthesize (approximately 8%), potentially a significant saving on the overall cell energy budget. Other researchers (Milligan & Morel, 2002) have suggested that the biogenic silica in diatom cell walls acts as an effective pH buffer, facilitating the conversion of bicarbonate to dissolved CO2 (which is more readily assimilated). Notwithstanding the possible advantages conferred by silicon, diatoms typically have higher growth rates than other algae of a corresponding size (Furnas, 1990)."

http://en.wikipedia.org/wiki/Diatom


It seems that diatoms make up over 70% of phytoplankton. Perhaps my tank wont bloom with phyto because im lacking silica?

What kind of silica would I use for this effect in some tank water in a bucket(to experiment) and also use it for the tank.

[Randy Holmes-Farley]

Well, it won't bloom with diatoms without it. It could bloom other organisms. :)

Sodium silicate is a fine additive. It is what I use:


Silica in a Reef Tank
http://advancedaquarist.com/issues/jan2003/feature.htm

[boxfishpooalot]

I love that article. I think I love biology or biochemsitry rather.

Do you add sodium silicate with your limewater?

I wonder if i could signifigantly reduce nitrates and phosphates with silicate additions? I did read that denitrifying bacteria prefer plant life as an organic sorce, I bet phytoplankton is the perfect size to settle in the sand.Although, I want to export phyto through skimming it should work both ways.What you think?

Im trying to super upgrade my export meathods somhow. I have read also that copepods feed exclusively on diatoms.

[Randy Holmes-Farley]

Do you add sodium silicate with your limewater?

No, I add it straight to the sump.

I wonder if i could signifigantly reduce nitrates and phosphates with silicate additions?

If diatoms are being limited by silicate, it might.

[boxfishpooalot]

Water glass is sold as sodium silicate, any ideas where that might be found? What other industries use sodium silicate that I could call to find some?

[Randy Holmes-Farley]

Hobby stores sometimes sell it.

[daytonians]

Randy,

I read your article on phoshates. IT WAS GREAT!!! Thanks so much.

I have one question. Is "Water Glass" a product name? If so, what is it used for in hobbies? May make it easier to find.

[Randy Holmes-Farley]

Water glass is a common name, like "gasoline". It is sodium silicate solution. It has been used for a variety of things that I do not know for sure, but I think it has been used for preserving eggs. It was also used in those growing rocks kits that were sold when i was a kid.

I read your article on phoshates.

Thanks. :)

[Sk8r]

The Chemistry Store . Com has it for 12.95 a gallon. What dosage, Randy?

[Randy Holmes-Farley]

From the above article:

"How much and what to dose?

I’d suggest dosing sodium silicate solution, as it is a readily soluble form of silica. It is very inexpensive. I initially used a high quality laboratory grade, but I’d expect the bulk grades sold to the world at large to be good enough (and I use it now). Remember, you aren’t dosing much, and the solutions available are very concentrated. You may find “water glass’ in certain stores because it is used by consumers for things like preserving eggs. Buying chemicals can be problematic for many people, however, and this hobby chemistry store 43 sells to individuals. Ten dollars (+ shipping) gets you enough to last 150 years of dosing with a 100-gallon tank, so cost is not an issue. I just ordered some from them myself and it came broken open, unfortunately. Some of you may have gotten Christmas presents that had ¾ of a gallon of sodium silicate solution coating them as they passed my package in the mail. Nevertheless, I still have enough for several years!).

Many “water glass” or sodium silicate solutions are sold with the concentration indicated by “° Baume”. Degrees Baume is a measure of the specific gravity, and values in the 40’s are typical of these concentrated solutions.44 A concentration of 41° Baume equates to 29% SiO2 by weight. Note that the density is high (1.38 g/mL for 41° Baume), so volume measurements should take this into account. Maybe eventually, some of the hobby supplement manufacturers will provide a supplement.

Safety note: Sodium Silicate solution is very basic (high pH). In fact, the pH can be substantially higher than limewater, so it is very corrosive to tissue and to metal devices. Be careful to not spill it on yourself, wear some eye protection, and if you spill it on something metal, wash it. In all cases, extensive washing with water is recommended in case of spills or exposure.

Based on my dosing experience, aquarists are probably safe dosing the equivalent of 17 mM (1 ppm SiO2) once every 1-2 weeks. That is based on the fact that my tank used that much in less than 4 days without having any sort of “bad” reaction. Of course, there’s nothing wrong with starting at a tenth of that and ramping up. And, of course, if you do get too much in the way of diatoms, just back off on the dosing. I presume that all that I added to my tank went into various organisms that us it (sponges, diatoms, etc), but perhaps I have more sponges than other aquarists, and diatoms consequently may be more of a concern in some tanks than in mine.

I’d also advise occasionally checking the soluble silica concentration in the water, in case the demand in your tank is substantially less than mine. If the concentration started to rise above 50 mM (3 ppm SiO2), even in the absence of diatoms, I’d probably reduce the dose rate because that is close to the maximum concentration that surface seawater ever attains.

Here’s how to determine dosing amounts. I’ll assume that you want 17 mM (1 ppm SiO2) dosing, and you can scale from there. If the concentration of the supplement is 29% silica by weight (41° Baume), then it is 290,000 ppm silica. To get to 1 ppm silica, you then need to dilute by 290,000 fold. If you add 1.3 grams of this supplement (0.96 mL) to a tank with 100 gallons (378,500 mL), then the final concentration will be about 17 mM (1 ppm SiO2). I’d disperse the concentrated silicate solution into some fresh water before adding it to the tank, and then add it to a high flow area. Because the pH is high, you likely will see some cloudiness that is mostly magnesium hydroxide. The magnesium hydroxide will dissolve without a problem, but to be safe, add the supplement in a high flow area."