How much sodium silicate to get 2ppm in 200mL?

[Randy Holmes-Farley Verified Community Expert]

Yeah, seen about a dozen users try the salifert kit on water with known Si addition and only like 1 reported it worked.
Was total zero for me as well.

Strange and disappointing.

 

[gbroadbridge]

Yeah, seen about a dozen users try the salifert kit on water with known Si addition and only like 1 reported it worked.
Was total zero for me as well.

Received the seachem silica test and it's telling me 3-4 ppm which is about what I dosed.

So the salifert test for some reason is faulty as it still indicates zero.

 

[Miami Reef]

@taricha @Randy Holmes-Farley

I did this experiment multiple times, and I saw a significant increase of phosphate each time.

I used a clean 2000mL beaker. Risned in RO/DI, filled with RO/DI and added Red Sea Blue Bucket salt until I got to 35ppt. I overshot the salinity to 1.030 s/g, so I diluted it to 1.026 s/g

I had the salt mixed with my magnetic stirrer.

Next, I tested the starting phosphates. I used both the Hanna PO4 ULR and the Hanna phosphorous checker. I used the Hanna PO4 ULR reagent for both checkers.

How did I test? I had 2 vials: one of them was rinsed with the clean beaker 35ppt solution a few times, then I did a final fill with 10mL. I added the PO4 ULR reagent to it and gently shook it for 2 min. Then I let it sit for 3 minutes.

While I waited for the timer, I did a 3x rinse and fill with the clean seawater from the beaker, and I filled the 2nd vial.

Once the 3 minute timer finished, I inserted the clean vial with no reagent added to both the checkers to clear C1.

Then I added the 2nd vial with the reagent added. The starting PO4 in the phosphorous checker was 5ppb, 7ppb, 5ppb.

In the PPM ULR checker, it was 0.03ppm, 0.02ppm, and 0.03ppm.

(I did 3 trials with the same 2 C1& C2 vials)


Next, I added about half a drop of sodium silicate. I let it stir for a few minutes, then I tested the silica with the hanna silica LR checker. I got 1.03ppm. I only tested it one time.

I saw minor magnesium hydroxide stirring around during the silica and phosphate trial 2 test.

For the second phosphate trial, I followed the same protocol above, and I used the same beaker with the 1ppm Si added.

Hanna PPB:
trial 1: 19
trial 2: 18


Hanna PPM:
Trial 1: 0.10
Trial 2: 0.08


@taricha @Rick Mathew


Please help me understand why our results were different? Yesterday I added about 7ppm of Si and the phosphate vial turned dark blue. I didn’t even bother checking. No matter how much I try, I can’t get Si to not show a false positive.

 

[Randy Holmes-Farley Verified Community Expert]

One possibility is actual phosphate in the silicate. A drop of sodium silicate in a vial would be quite a large dose.

 

[Miami Reef]

One possibility is actual phosphate in the silicate. A drop of sodium silicate in a vial would be quite a large dose.

I added a drop of sodium silicate to 2L.

I just tested phosphates again:

Hanna ppb checker with ppm ULR reagent
Trial 1: 26ppb
Trial 2: 26ppb

Hanna ppm ULR checker with ppm ulr reagent

trial 1: 0.09ppm
trial 2: .11ppm


The starting phosphate was about 0.02ppm and 5ppb in the same water before adding 1ppm silica.

I’m going to test the silica level in the 2L solution to make sure it really is 1ppm

@Randy Holmes-Farley im using a high purity grade of silica to specifically avoid phosphates. It says 99.9% pure by Loudwolf, a reputable company

 

[Randy Holmes-Farley Verified Community Expert]

Ok, I thought maybe you were adding it directly into the vial of the phosphate test.

 

[Garf]

I added a drop of sodium silicate to 2L.

I just tested phosphates again:

Hanna ppb checker with ppm ULR reagent
Trial 1: 26ppb
Trial 2: 26ppb

Hanna ppm ULR checker with ppm ulr reagent

trial 1: 0.09ppm
trial 2: .11ppm


The starting phosphate was about 0.02ppm and 5ppb in the same water before adding 1ppm silica.

I’m going to test the silica level in the 2L solution to make sure it really is 1ppm

@Randy Holmes-Farley im using a high purity grade of silica to specifically avoid phosphates. It says 99.9% pure by Loudwolf, a reputable company

I found this finding interesting so I’ve replicated it with my no brand sodium silicate and Hanna LR. I got a big fat zero.

 

[Miami Reef]

I found this finding interesting so I’ve replicated it with my no brand sodium silicate and Hanna LR. I got a big fat zero.

@Idech said the interference showed with the ULR, but not with the LR. I don’t have the LR to test it.

I tested the silica in my 2L test container. It is showing 2ppm (showed 1ppm yesterday)


One things for certain, the Hanna LR silica tester was stated for freshwater only. It probably makes sense to keep it for FW only. It’s not very consistent.

But it shows 1-2ppm in the vial, and I saw a clear rise of phosphates. I don’t know if it’s from an interference or from added impurities. But something is causing a higher PO4 reading in my ULR checkers when adding silica.

 

[Miami Reef]

I found this finding interesting so I’ve replicated it with my no brand sodium silicate and Hanna LR. I got a big fat zero.

Hey buddy,

How many ppm si did you dose in your trial? Do you have a link to the exact silica product?

I’m hoping it’s just my silica brand that was bad. I dont want to stop dosing silica.

 

[Garf]

Hey buddy,

How many ppm si did you dose in your trial? Do you have a link to the exact silica product?

I’m hoping it’s just my silica brand that was bad. I dont want to stop dosing silica.

Not got a silica test kit but it was one large drop (the drippage off the end of a steak knife, lol) of this stuff, in two litres;

Ahh - won’t let me post the link.

How about a pic, lol;

 

[Miami Reef]

Not got a silica test kit but it was one large drop (the drippage off the end of a steak knife, lol) of this stuff, in two litres;

Ahh - won’t let me post the link.

How about a pic, lol;

I tried many ways to search for this product on Amazon to no avail. Maybe it’s not available to the states?

Maybe @taricha can tell me where he bought his.

 

[Simon_M]

Deleted.

 

[Simon_M]

I tried many ways to search for this product on Amazon to no avail. Maybe it’s not available to the states?

Maybe @taricha can tell me where he bought his.

This is a UK Company, so they may not be selling it in US. In UK it is available from amazon.co.uk or eBay.co.uk

There are many US sellers of 40% Sodium Silicate on eBay.com

I have a small sample bottle with the data sheet from the UK company.

I have added a total of 3ml to 550 litres yesterday and today. It should measure 3*.29 * 1000000 / 550000 ppm = 1.6 on day 1 and less than 3.2 on day 2.

With Salifert Silicate Test Kit it reads 0 with 4 tests.

 

[taricha]

Received the seachem silica test and it's telling me 3-4 ppm which is about what I dosed.

So the salifert test for some reason is faulty as it still indicates zero.

Thanks! good to know that seachem's Silicate kit is usable for the ~ppm Si range.

With Salifert Silicate Test Kit it reads 0 with 4 tests.

yep. Salifert Si test seems consistent, at least. Almost always detects ~0% of dosed Si.

One things for certain, the Hanna LR silica tester was stated for freshwater only. It probably makes sense to keep it for FW only. It’s not very consistent.

I don't doubt your results. I just know that Rick and I found Si checker to be rock solid for us.
I've used Brightwell Spongexcel for most of the checking with Si and PO4.

Here's how hanna Si checker compared to ICP and calculated additions.
X- axis is the calculated Si addition from spongeexcel, the black line indicates expected value if the stock and my additions were perfect and the Instant ocean had no Si in it.
Red is hanna checker (circles initially, triangles were retest weeks later after ICP results)
Blue, green, yellow, and purple are four ICP vendors.

The hanna results and 3 of 4 ICP vendors agreed pretty closely that the Si level was nearly that expected from the label concentration on the bottle of spongexcel.



Anyway, back to the topic.

But it shows 1-2ppm in the vial, and I saw a clear rise of phosphates. I don’t know if it’s from an interference or from added impurities. But something is causing a higher PO4 reading in my ULR checkers when adding silica.

Two ideas.
first, any chance you are using the same hanna cuvettes between your Si tests and your PO4 tests? I find the PO4 test can sometimes be thrown off if I try to use a vial I've run other tests in. No matter how many times I rinse it.

second, I think that the Si source may also be a possibility. I don't remember Rick's Si source, but he didn't use the loudwolf waterglass product either.

 

[Miami Reef]

first, any chance you are using the same hanna cuvettes between your Si tests and your PO4 tests? I find the PO4 test can sometimes be thrown off if I try to use a vial I've run other tests in. No matter how many times I rinse it.

I used the same Hanna cuvettes for every single trial except for the very last one.

I got almost a 100% replication from these 2 results.

Testing Si same day vs next day resulted in a 1ppm increase on the next day.

PO4 was around 0.03ppm, and it went to about 0.10ppm, that’s assuming the Si is around 1-2ppm with the Si checker.


I always use the same vial when testing Si. For PO4, I only ever started using 2 different vials when using the ppb checker, but the results between 1 vs 2 vials and 1st vs 2nd trial were identical.

 

[Miami Reef]

Forget it. I tried doing the experiment, but I saw a lot of inconsistencies with the checkers.

I tested Silica right after dosing: 0.80ppm.

The next morning: 1.80ppm.

Phosphates did appear to rise after dosing Si.

Last night it was 0.11, this morning it was 0.08ppm (started at 0.03ppm)

Let’s just pretend this thread never existed.

I added a drop of sodium silicate to 2L.

I just tested phosphates again:

Hanna ppb checker with ppm ULR reagent
Trial 1: 26ppb
Trial 2: 26ppb

Hanna ppm ULR checker with ppm ulr reagent

trial 1: 0.09ppm
trial 2: .11ppm


The starting phosphate was about 0.02ppm and 5ppb in the same water before adding 1ppm silica.

I’m going to test the silica level in the 2L solution to make sure it really is 1ppm

@Randy Holmes-Farley im using a high purity grade of silica to specifically avoid phosphates. It says 99.9% pure by Loudwolf, a reputable company

 

[Miami Reef]

first, any chance you are using the same hanna cuvettes between your Si tests and your PO4 tests? I find the PO4 test can sometimes be thrown off if I try to use a vial I've run other tests in. No matter how many times I rinse it.

Oh, I misread this. Yes, I 100% used to same cuvettes between tests. I just rinse it with RO/DI.

That’s a very good point. I don’t have different vials for separate tests. I never considered doing that. Hmm. I wonder if that’s what’s causing my issues? I use the same vials for PO4, NO3, and Si.

I thought you were referring to using 1 vial for both C1 and C2 for the PO4 test.

 

[taricha]

Oh, I misread this. Yes, I 100% used to same cuvettes between tests. I just rinse it with RO/DI.

That’s a very good point. I don’t have different vials for separate tests. I never considered doing that. Hmm. I wonder if that’s what’s causing my issues? I use the same vials for PO4, NO3, and Si.

This is a good habit that saves me headaches, to have a couple of cuvettes dedicated to each separate test kit chemistry. When I can't, I have to accept that the first couple of tests may look different than the tests that follow it.
Having said that, I don't think that's the likeliest issue with your phosphate results, since they were identical in three straight tests. I lean more towards the water glass product being different than the various Si sources that me, Rick, and Garf looked at.

 

[Miami Reef]

This is a good habit that saves me headaches, to have a couple of cuvettes dedicated to each separate test kit chemistry. When I can't, I have to accept that the first couple of tests may look different than the tests that follow it.
Having said that, I don't think that's the likeliest issue with your phosphate results, since they were identical in three straight tests. I lean more towards the water glass product being different than the various Si sources that me, Rick, and Garf looked at.

Can I make a muriatic acid solution to clean my vials? Would that reset them to scratch? I want accurate results.

 

[Simon_M]

The Salifert test drawing a blank is puzzling:

1. Silicate to be dosed isn't what it claims to be?
2. Test kit is not working?
3. Type of Silicate isn't being detected?
4. Adding it to the tank causes it to immediately precipitate out?
5. Silicate binds to something immediately?
6. It's a freshwater and not saltwater test kit?

I'm going to try mixing RODI with known (probably) concentration high/low to test again.

Also mixed RODI and salt and repeating the test.

I'm also going to buy a bottle (not a LFS sample bottle) of the Silicate. Is Water Glass much more viscous than water? Perhaps I have was sold a placebo?

For now, with no way to dose and test I'm looking for guidance e.g. can you keep applying the recommended dosage of 2-4 ppm every few days? The Hanna Silicate Testers don't seem to be available to buy in UK - otherwise I would be tempted to get one.