Best silicate tester

Dami2205

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What is the Best silicate tester with out having to send ICP?? I’m fighting diatoms that have created a Bio film to live its more than a bad diatom bloom they found a way to créate a bio film to live with in.
 
What is the Best silicate tester with out having to send ICP?? I’m fighting diatoms that have created a Bio film to live its more than a bad diatom bloom they found a way to créate a bio film to live with in.
Just to add my TDS is 0 but they are growing like crazy 3 weeks now and the bio film is the thing that worries most they are consuming silicate s like crazy, sand was new live sand by Fiji pink araga live and rocks were new Aqua forest, so I just need to make sure silicates are not in water, please help.
 
Are you sure it's diatoms and not dinoflagellates or chrysophytes and have you verified this with a microscope?
Maybe you can add some photos of the biofilm you are talking about (preferably under white light) so the community can analyze the situation a bit better 🙂
 
Are you sure it's diatoms and not dinoflagellates or chrysophytes and have you verified this with a microscope?
Maybe you can add some photos of the biofilm you are talking about (preferably under white light) so the community can analyze the situation a bit better 🙂
I’m sure only diatoms penate



2026-08-17-15-04-10-533.jpeg

2026-08-17-15-06-53-504.jpeg
 
I agree that there are diatoms in the video, but I can't identify the brown mat at the bottom of the image. It's very possible to have multiple nuisance algae issues at once, so I'm not sure if diatoms are actually the core problem.

If you compare the density in your video to that of post #16 (page 1) in my microscopy thread, you will see that the density of diatoms around the actual mat should still be quite high (see video; if you are using the app, you will have to use a web browser instead, as videos are currently broken), and yet the mat on the substrate is still quite limited (first image of the post).

The "knot" of diatoms is what actually becomes visible to the naked eye as biofilm, so we need to verify that the brown mat is actually a knot of diatoms and not something else.

Regarding the test: You can try Salifert. I think it has a detection limit of approx. 0.03ppm.
 
I agree that there are diatoms in the video, but I can't identify the brown mat at the bottom of the image. It's very possible to have multiple nuisance algae issues at once, so I'm not sure if diatoms are actually the core problem.

If you compare the density in your video to that of post #16 (page 1) in my microscopy thread, you will see that the density of diatoms around the actual mat should still be quite high (see video; if you are using the app, you will have to use a web browser instead, as videos are currently broken), and yet the mat on the substrate is still quite limited (first image of the post).

The "knot" of diatoms is what actually becomes visible to the naked eye as biofilm, so we need to verify that the brown mat is actually a knot of diatoms and not something else.

Regarding the test: You can try Salifert. I think it has a detection limit of approx. 0.03ppm.
After to RO/DI unit the silicate test should read 0?? What is the value I can expect?? Just to have a number and start from there Also if test the water on the display what can I expect to look at??
In regard the mat is so thick I cant break it down from the sand that is why you can see the sand on the pics and videos.
 
After to RO/DI unit the silicate test should read 0?? What is the value I can expect?? Just to have a number and start from there Also if test the water on the display what can I expect to look at??
In regard the mat is so thick I cant break it down from the sand that is why you can see the sand on the pics and videos.
Your RO/DI should obviously measure 0ppm TDS using an appropriate pure water tester. The silicate levels in your tank can still differ because silicate can be introduced through for example frozen fish food and the substrate. The Salifert test could be able to help you, if you don't want to get an ICP test.

Okay. if the mat isn't just loose slime that is a good indicator for diatoms. There are silicate adsorbers but they will also remove phosphate (or vice versa, phosphate adsorbers will also remove silicate), so if your tank is low on phosphate you can try to counter with phosphate dosing ,or try if a product like Fauna Marin Phos 0.04 is capable of removing enough silicate from your system. It's something I wanted to ask Randy anyway, maybe he has a second.

Hey @Randy Holmes-Farley, you certainly remember "Fauna Marin Phos 0.04" which promises to not drain phosphate below 0.04ppm. You explained how they probably saturated sites on the adsorber in a way that those strong enough to adsorb below 0.04ppm are saturated, while the residual sites are not saturated. Do you know how this translates to silicates? I assume the binding energy is different between phosphate and silicates, so will Phos 0.04 be able to drain silicate below 0.04ppm or only above? 😁
 
Your RO/DI should obviously measure 0ppm TDS using an appropriate pure water tester. The silicate levels in your tank can still differ because silicate can be introduced through for example frozen fish food and the substrate. The Salifert test could be able to help you, if you don't want to get an ICP test.

Okay. if the mat isn't just loose slime that is a good indicator for diatoms. There are silicate adsorbers but they will also remove phosphate (or vice versa, phosphate adsorbers will also remove silicate), so if your tank is low on phosphate you can try to counter with phosphate dosing ,or try if a product like Fauna Marin Phos 0.04 is capable of removing enough silicate from your system. It's something I wanted to ask Randy anyway, maybe he has a second.

Hey @Randy Holmes-Farley, you certainly remember "Fauna Marin Phos 0.04" which promises to not drain phosphate below 0.04ppm. You explained how they probably saturated sites on the adsorber in a way that those strong enough to adsorb below 0.04ppm are saturated, while the residual sites are not saturated. Do you know how this translates to silicates? I assume the binding energy is different between phosphate and silicates, so will Phos 0.04 be able to drain silicate below 0.04ppm or only above? 😁
The thing is I want to dispare issues on my RO/DI unit, so after the RO/DI silicates should read 0 right??

And I want to test my display just in case the RO/DI unit is working fine, just to see if there is something on my tank producing silicates, if its the fish food I would need add way to much to produce that much silicates to Fede that much diatoms here are com pics of the film I manage to produce.

PO4 las week was .03
PO4 today is .04 since I feed a little more to rise it up.



2026-08-17-16-23-02-860.jpeg

2026-08-17-16-21-46-208.jpeg
 
I'm not sure how the Salifert Si-Test works (haven't looked into the chemistry yet), but I could imagine you would have to mix it to saltwater first before the test works properly. But at least this way you would also test your salt mix for silicate pollutants 😅

The images might really show knots of diatoms, so it's likely the issue. Note however that they don't need much so don't underestimate what a few ppb can do, especially if your substrate is still leaking silicate. Is the tank new or did you add new sand recently? This is usually when diatoms appear again.

But obviously it's possible that your RO/DI system has depleted DI-resin or that the water dug a tunnel through the resin and your TDS meter is simply failing.
 
The thing is I want to dispare issues on my RO/DI unit, so after the RO/DI silicates should read 0 right??

And I want to test my display just in case the RO/DI unit is working fine, just to see if there is something on my tank producing silicates, if its the fish food I would need add way to much to produce that much silicates to Fede that much diatoms here are com pics of the film I manage to produce.

PO4 las week was .03
PO4 today is .04 since I feed a little more to rise it up.



2026-08-17-16-23-02-860.jpeg

2026-08-17-16-21-46-208.jpeg

No. Ro/di will remove most silicate, and two DI in series will do an even better job, but some silicate will typically get through. It’s a hard ion to get down to very low levels, but fortunately there’s not typically a need to, and ensuring that tds is 0 ppm will generally ensure there is little enough silicate in the ro/di to prevent pest levels of diatoms.
 
No. Ro/di will remove most silicate, and two DI in series will do an even better job, but some silicate will typically get through. It’s a hard ion to get down to very low levels, but fortunately there’s not typically a need to, and ensuring that tds is 0 ppm will generally ensure there is little enough silicate in the ro/di to prevent pest levels of diatoms.
So Randy and the other person what is to do next how do fight this things?? How do I deplete the silicates or how do I get rid of the diatoms?? Any suggestions??
 

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