Silicate test doesnt measure anything

[Cory]

So my Salifert silicate test doesnt measure any silicate even after adding sodium silicate (water glass). Why?

I tested my tank and it read 0ppm silicate. I dosed 5ml of sodium silicate to 200 gallons and waited 5 mins for it to circulate, and it still read 0ppm. Why?

 

[Randy Holmes-Farley]

Well, let’s calculate roughly what it might be. 5 mL might be 2 g of silicate, so you dosed about 2000 mg/750 L —> 2.7 ppm. You should detect that. My kit did when I dosed a similar amount.

maybe the kit isn’t working, or the wrong product is in the bottle.

 

[Dan_P]

So my Salifert silicate test doesnt measure any silicate even after adding sodium silicate (water glass). Why?

I tested my tank and it read 0ppm silicate. I dosed 5ml of sodium silicate to 200 gallons and it waiting 5 mins for it to circulate, and it still read 0ppm. Why?

Let’s pull in @taricha on this discussion.

There is a distinct possibility that most hobby kits will not detect silicate. The low range silica Hanna Checker was the only one I found that did. Also, dosed silicate can disappear rather quickly, so, for your first measurement, don’t wait too long between dosing and measuring the silicate level.

To test your kit, dose silicate to a sample of tank water and measure it immediately. If your kit is any good, you should measure the expected level. You might have to dilute your silicate with RODI water to dose a small amount of tank water.

 

[Randy Holmes-Farley]

Not sure what you mean. What do you think they do detect? The Hach kit certainly detected silicate when I dosed it.

 

[Randy Holmes-Farley]

http://web.archive.org/web/20130221143953/http://advancedaquarist.com/issues/jan2003/feature.htm

Figure 4. The concentration of soluble silica as a function of time after dosing. Dosing was done at t=0. The concentration for t=0 (30 uM) is an estimate based on what was added and the estimated total system volume.

Measuring Silica
Before going on to discuss silica in reef tanks, a few comments on measurements of silica seem worthwhile. In the context of organisms that use silica, we are only interested in soluble forms of silica, typically silicic acid and silicate. Ignoring the fact that there can actually be other soluble forms in certain situations, like extended chains or rings, the most important distinction that reef keepers need to be aware of is between tests that analyze for silicon, regardless of form, and those that analyze for soluble silica.

Tests that analyze for silicon, such as ICP (inductively coupled plasma) can include silica particulates (e.g., fine sand) in the result. Even with filtration, fine particles can evade removal. Consequently, it is complicated to extrapolate from an ICP measurement to a soluble silicate concentration. In Ron Shimek’s tests of aquarium water,29 for example, the technique chosen was ICP. Consequently, people should not interpret the values obtained, 1.8 to 104 mM (0.05 to 2.9 ppm Si = 0.11 to 6.2 ppm SiO2 ) as necessarily indicating anything about the dissolved silica concentration present in the tanks studied (except that the dissolved silica cannot exceed those numbers).

Similarly, in studies of salt mixes,30 the different forms may be an issue as well. In that case, the authors attributed differences between ICP and wet chemistry methods to the nature of the silicon present.

Tests that analyze for soluble silica, such as any of the kits available to the hobby, will only detect soluble forms. I recommend the low range silica test from Hach, Model SI-7, catalog number 22550-00. While the values obtained with such kits may not be comparable to those obtained by other methods, they are suitable for understanding how much dissolved silica is present and available to organisms in tank water, and in other aqueous solutions, such as tap water.

 

[taricha]

There is a distinct possibility that most hobby kits will not detect silicate. The low range silica Hanna Checker was the only one I found that did.

Not sure what you mean. What do you think they do detect? The Hach kit certainly detected silicate when I dosed it.

Among people who've dosed Si, salifert kits have been successful in one out of over a dozen cases I've seen posted here. It was zero for a dozen+ (including Dan and myself), and then someone just recently reported it works perfectly for them. So maybe Salifert tweaked their kit?
Hanna low range silica tester has been flawless (maybe 10% under-measure) despite claiming its not for SW, and I'm sure hach is at least as good.

 

[Cory]

Thanks guys. Ive seen a few posts about other people saying it doesnt measure anything- online reviews.

Iirc it measured it before when the kit was new. Like 3 months ago. The kit expires 06/2020.

Is a kit like this sensitive to expiration?

Only thing i added previously was potassium and amquel ammonia remover.

The kit says it measures silicon oxide. Would sodium silicate form that instantly?

 

[Randy Holmes-Farley]

I wouldn’t rely on that sentence since it is translated and could cover a multitude of incorrect assumptions on what it detects.

 

[Cory]

I wouldn’t rely on that sentence since it is translated and could cover a multitude of incorrect assumptions on what it detects.

Okay ill ignore it. I tested again and it doesnt detect anything.

 

[Randy Holmes-Farley]

Okay ill ignore it. I tested again and it doesnt detect anything.

Maybe we can get Habib Sekha of salifert to pop in and give some commentary.

 

[Cory]

@Habib(Salifert)

Any help?

 

[4theluvofcoral]

What kit did you use Randy?

Well, let’s calculate roughly what it might be. 5 mL might be 2 g of silicate, so you dosed about 2000 mg/750 L —> 2.7 ppm. You should detect that. My kit did when I dosed a similar amount.

maybe the kit isn’t working, or the wrong product is in the bottle.
[/QUOTE

 

[4theluvofcoral]

Has anyone used the test by Seachem?
"SeaChem Multitest: Silicate Test Kit"

This kit measures silicates down to 0.5 mg/L in marine or freshwater.

• multi-cavity plate for simultaneous testing of up to 6 tests at the same time
• sensitive to less than 0.5 mg/L
• includes reference for test validation
• marine or fresh water
• Range: 0 - 25 mg/L
• Precision: 0.1 - 1 mg/L & 0.01 - 0.1 mg/L

 

[Randy Holmes-Farley]

What kit did you use Randy?

I used the low range silica test from Hach, Model SI-7, catalog number 22550-00.