Grow-Sil for silica, is it any good?

Chris Edward

Well-Known Member
Hello all,

I just recently found out about this stuff called Grow-Sil, which is made from rice hulls and boasts a soluble silica amount of 99.9% and a pH of 7.0
Has anyone used this before?
Is it like AgSil-16H?

It appears I can swap the two out and use about half as much of the Grow-Sil as I was using of the AgSil-16H and it won’t have as big an effect on pH, which is always a plus.

I was using Grotek Pro-silicate, but then I found AgSil-16H, which is the same thing (potassium silicate), but in powder form and it costs 56% less.
A 1 liter bottle of Pro-silicate costs about $15.
A 1 pound bag of AgSil-16H costs $20 and can make 3 liters.

AgSil-16H has about 52% soluble silica and 4% potassium and the mixture is very alkaline, so you have to add it to your source water first, then add pH down and then add your fertilizer.
If you add the fertilizer first, then add the AgSil-16H, it will cause some nutrients to fall out of solution (namely calcium).

If I can swap out the Grow-Sil then this would be an additional 47% savings on the AgSil-16H, so the per liter cost will go down to something like $3.54

That would be awesome!
I use a lot of silica…

While we’re all here, what silica do y'all use?
How does it work for you?

Thanks for your help…


Well-Known Member
Isn't Gro-Sil more of a soil additive and not really intended as a water soluble fertilizer component? You are growing in coco aren't you?

I've used the AgSil but now it sits unused. I'm not a silica proponent. I've never noticed any significant benefits from using silica additives. A good base nutrient regimen provides everything a plant needs. It won't hurt anything but I prefer to keep things as simple as possible. The only additive I use is water soluble humic/fulvic acid and potassium sulphate early in flower for a couple of weeks if I remember to add it.

AgSil can be problematic when mixing with other nutrients and should be used at half strength at most. It caused some minor issues when I used it. That's why it sits unused on a shelf.


Chris Edward

Well-Known Member
Silicate is for both soil and hydro.

No, I don’t grow in coco.
Everyone seems to think I do…
I use modular Dutch buckets with hydroton as the media.

If the silica isn’t added at the right time during mixing, it can cause nutrients to fall out of solution.
So I just add it to the source water, then I add pH down to bring the water back in range and then I add fertilizer.

The reason I started this post is because I wanted to know if Grow-Sil was more for soil or hydro, what people thought of it, how soluble it is, etc…
Because the website for Grow-Sil just gives generalities. It says it has “high" solubility, whatever that means…
I am also waiting for the company to get back to me and clear some things up, but because it’s between Christmas and New Year's I doubt they will get back to me before 2019.
What caught my eye was that it is 99.9% silica and it has a pH of 7, so I won’t have to be as careful about mixing it, the way I am with the AgSil-16H.

If you don’t mind me asking…
How were you using the AgSil-16H?
What issues did it cause?

Do you grow in soil or hydro?
The additions of humic/fluvic acid suggest hydro, but I am curious why you add these, because this is typically something added to aquaponics systems to keep algae growth down.
Is it for root stimulation?

You also mention adding potassium sulfate for the first few weeks of flower.
Do you also cut the nitrogen (and calcium) back during flower?

Thanks for letting me pick your brain…


Well-Known Member
I was using the silica after reading numerous posts about it's use. I rarely change from my standard feeding solution but I thought I'd give it a try and see if it made any difference. The issues it caused were a yellowing and curling of some of the leaves. Something that never happened when I didn't add it. It could be that I used too much. I grow in coco so it could be that it effected the pH significantly causing nutrient lockout. I haven't used it since.

I use the humic/fulvic acid as it's supposed to help with nutrient uptake. It might not do what I think it's doing but there is no negative effect from using it and it's extremely inexpensive since I buy it in soluble powder form by the pound. I don't spend money on the bottled products available because they are just the same thing mixed with water.

I don't cut back the nitrogen specifically. I cut back the overall strength of the nutrient solution starting about halfway through flower tapering it down until harvest. I still keep the same ratio's of the three part nutrient I use which is just calcium nitrate, micronutrients, and monopotassium phosphate.

Chris Edward

Well-Known Member

AgSil-16H is really alkaline (I have never tested the stock solution), but 1 tsp to a gallon of the stock solution can take source water that has a pH of 5.9-6.0 and tip up to well over 7.0.
So when I make up a new batch or top off batch of fertilizer I will add the silica first, then I add pH down so the pH comes back to within normal range. Then I will add my regular fertilizer components and the pH usually stay around 6.3 or so.
Then again all of that may be moot because coco is it’s own animal, and what seems to work for other media doesn’t with coco.
I am not knocking coco, I used to use a lot of it when I had a garden outside, it’s great stuff.
Worms love it!

The AgSil-16H powder is usually made into a 7-10% stock solution and then 1 teaspoon of this stock solution is used per gallon, which should give you around 100ppm’s of silica per gallon.

I use both silica and magnesium sulfate similarly to how you use the humic/fluvik acid, to help with nutrient absorption.
As well as other things…
The magnesium sulfate also helps balance out the calcium from the calcium nitrate, so there is no nutrient lockout issues.

I am like you, I buy all my fertilizer in powder form, this way they keep forever and I am not paying some crazy high price for a bottle of fertilizer or supplement that is like 75% water.

I have never used monopotassium phosphate on it’s own. I have used it as part of a matrix of fertilizer (a commercial powder mix) before though and it is great stuff!

What form(s) of nitrogen do you use?
I am using potassium nitrate and calcium nitrate, I would also like to incorporate some ammonium sulfate into the mix because the plants really don’t need all the calcium that the calcium nitrate provides and ammonium sulfate has more available nitrogen, so I won’t have use as much.

Eventually I would like to come up with my own formula, not to sell, but just to fine tune for my plants.
I like tinkering with stuff like this, it keeps my brain busy.

Happy New Year!!!

radiant Rudy

Well-Known Member
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