Silica for Sponges & Diatoms

[Subsea]

My mixed garden macro tank has ornamental sponges that I purchased but also some that grew off live rock. The water is this tank is saturated with silica but no diatoms. Competition for food & predator behavior from diversity of life forms might explain lack of diatoms.

@Randy Holmes-Farley
Is silica consumed by other marine organisms beside diatoms & sponges?

I have used a regional agriculture lab for macro and water analysis, but never considered testing for silicates in macro.

Water Analysis

Ever wonder what’s in your water? An accurate water test is the first step to protecting plant, animal and human health. For Farmers & Ranchers How do common chemicals and minerals affect crops and livestock? Crops can suffer from exposure to irrigation water that contains high levels of soluble...

www.wardlab.com

Gracilaria Parvispora
N at 2.59%
P at 0.082%
K at 13.54%
Ca at 0.555%
Mg at 1.163%
S at 4.81%
Zn at 139ppm
Fe at 107ppm
Mn at 20ppm
Cu at 7ppm

 

[Spare time]

Following! I was thinking of dosing silica too after my yellow sponges all disappeared (they all looked like they had a single bite taken out and I thought I caught my blenny munching on one but I have a wantenabei angelfish too). I am guessing my silica dropped since I became more strict on my TDS from my RO unit.

Here is randy's silica page. I hope this helps in the mean time till randy gets here!

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

 

[Subsea]

Following! I was thinking of dosing silica too after my yellow sponges all disappeared (they all looked like they had a single bite taken out and I thought I caught my blenny munching on one but I have a wantenabei angelfish too). I am guessing my silica dropped since I became more strict on my TDS from my RO unit.

Here is randy's silica page. I hope this helps in the mean time till randy gets here!

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

Outstanding write up. Thank you for the link. I liked this paragraph,

[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.]

 

[Subsea]

My tank is super saturated with silica. Make up water is 1000’ deep groundwater from Trinity Aquifier which was a shallow inland sea that was full of diatoms.

 

[Spare time]

My tank is super saturated with silica. Make up water is 1000’ deep groundwater from Trinity Aquifier which was a shallow inland sea that was full of diatoms.

That "tree" is awesome

 

[Subsea]

Thank you. Original Tonga Tree was manufactured. Then GSP ran wild so much so that it cantilevered out at the top, shading 40% of tank. Last month Tonga Tree got a GSP hair cut. I also added two 4’ led lights bars to assist with light requirement of gorgonian.

 

[biophilia]

One thing to keep in mind is that only some sponges utilize silica to build the spicules that give them structure. Some use calcium carbonate and many others build spicules out of collagen proteins.

That being said, I'm a big advocate for dosing silica in reef aquariums and have never really seen appreciable diatom growth even when dosing it daily via a dosing pump to maintain somewhere around natural seawater levels.

Something interesting I did find when I initially began dosing was that I had an explosion of siliceous sponge growth for a month or two followed by many of those sponges disappearing as quickly as they came. I'm unsure why the population crash occurred, but I'm guessing it had something to do with a lack of food for the sponges to eat in the water column. In the future I'd really like to experiment with adding some sort of planktonic cyanobacterium like Synechococcus sp. for the sponges to feed on (or even just dosing astaxanthin powder since it's just dehydrated cyano)... maybe more acetic acid also.

Beyond snails, most of the diatoms are likely consumed by copepods as quickly as they grow, but something I've wondered is how that dynamic plays out over time. There is some research showing that diatom/silica rich diets can slow the reproductive rate of copepods over time.

 

[Randy Holmes-Farley Verified Community Expert]

My tank is super saturated with silica. Make up water is 1000’ deep groundwater from Trinity Aquifier which was a shallow inland sea that was full of diatoms.

Supersaturated? Really?

Or just very high?

Do you know the solubility limit of silicate in seawater?

 

[Subsea]

Saturated.

Supersaturated? Really?

Or just very high?

Do you know the solubility limit of silicate in seawater?

My bad for the embellishment. Silica is very high.

when I dripped sodium silica into tank, the liquid drops crystallized. I do not know the solubility limit in seawater, but I may be there.
I will send off sample of tank water and Aquifer water for testing silica. I will request Ward Lab silica test protocol. Ward Lab is a regional agriculture lab. Is there a specific test that you recommend?

 

[Randy Holmes-Farley Verified Community Expert]

The cloudiness when dosing is likely magnesium hydroxide.

 

[SMSREEF]

The cloudiness when dosing is likely magnesium hydroxide.

I am stumped and don’t trust goggling answers.

How much silica is soluble in saltwater?

What would be the upper limit of beneficial silica level in a reef tank?

What level do you think a form of silica removal is necessary in a reef tank?

 

[Subsea]

This is Trinity Aquifer water analysis (standard household test for $27) from 6 years ago. I sent Ward Lab a request for test protocol for iodine & silicates. I will wait till after Christmas rush to ship off water samples.

 

[Randy Holmes-Farley Verified Community Expert]

I am stumped and don’t trust goggling answers.

How much silica is soluble in saltwater?

What would be the upper limit of beneficial silica level in a reef tank?

What level do you think a form of silica removal is necessary in a reef tank?

Don't overthink this.

There is no level, IMO, that requires removal unless diatoms are a serious ongoing problem. it does not cause any other problems that I am aware of.

For folks who have very high and ongoing levels of Si determined by ICP, I would not automatically assume the form is the main form present in seawater Si(OH)4/ silicate. There are other forms that could be there, including various cyclic rings of silicon and oxygen. There may also be colloidal (very tiny particulate) forms of SiO2 present.

As to the solubility of SiO2 in seawater, I think that comes more into play for dissolving glass and sand than for limiting Si levels, but here is my discussion on that topic:

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

"Silica sand is largely composed of quartz. Quartz has a maximum solubility in pure freshwater of about 180 uM (11 ppm as SiO2), and is somewhat higher in seawater"

"Based on my dosing experience, aquarists are probably safe dosing the equivalent of 17 uM (1 ppm SiO2) once every 1-2 weeks. "