(Super) Silicate passing by all resins

PBar · Dec 8, 2020

Dear colleagues,
I hope everything is fine with you all.

I can’t get zero silicate in the RO water.
My main concern is linked to a diatoms issue that I’m having in the tank.

What really puzzles me is the fact that I’m using now a “huge“ RO/DI system:
1 x sediment filter 10 micron
2 x carbon
1 x RO membrane AquaMedic
3 x RO resin AquaMedic
1 x Silicate remover Vertex

Flow: 6 liters per hour.

The last ICP test from ATI displayed for Silicon:
RO - 31.22 µg/l
Tank - 238.9 µg/l

If I understand correctly, if all of the silicon is bound in silicate, I need to multiply the result by ~3,2 to get the value for silicate.

Any suggestions? Am I missing something?

Just as info: new house (new country) + new filter. As such, It’s been a year and I never managed to solve silicate. I‘ve already changed all all resins to be sure.
Similar (smaller) filters systems in the past would easily get rid of Silicates.

Thanks in advance!

Randy Holmes-Farley · Dec 8, 2020

Welcome to Reef2Reef!

I understand the concern about diatoms, but those silica levels are not particularly high. I dosed my tank substantially higher than that once a week to support sponges and diatoms.

I assume the effluent of the RO/DI read 0 ppm TDS?

How old is the tank?

PBar · Dec 8, 2020

Dear Randy,
thanks a lot! I’m a big fan of you for a long time!

Tank is running already for almost a year.
Indeed, TDS is zero.

I agree, but another point: it is a very shallow tank for SPS - 100 gal.
220 x 45 x 30 cm
Combined with the huge circulation, it evaporates near 10% per week.

Is it enough to fuel the diatoms?

Randy Holmes-Farley · Dec 8, 2020

PBar said:
Dear Randy,
thanks a lot! I’m a big fan of you for a long time!

Tank is running already for almost a year.
Indeed, TDS is zero.

I agree, but another point: it is a very shallow tank for SPS - 100 gal.
220 x 45 x 30 cm
Combined with the huge circulation, it evaporates near 10% per week.

Is it enough to fuel the diatoms?

Diatoms will likely grow if the silicate is at the level you report in the tank, but ICP cannot identify the form of the Si.

Have you ever measured silicate in your tap water to see what the starting level is?

The amount you are adding at 10% evaporation a week ( 3 ug/L addition to the aquarium) is much less than I dosed to my tank, and I'm not sure how I see the tank getting to 238 ug/L Si in the tank by evaporation top off. If you started at no Si (or even 31 ug/L to match the RO/DI), it would take years to reach the level you report in the tank, and that assumes no consumption.

My tank consumed 10 micromole/L (280 ug/L) Si in one day after dosing (see below)

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

PBar · Dec 8, 2020

Randy,
thanks for the quick reply.

But now reading your article, I’m a bit “lost”.
(Thanks a lot for the indication)

Indeed, it can’t be related to the current RO.

I double checked my ICP test (from September) and the level of Silicon in the RO was 349 µg/l.
It was before I add the third Resin stage plus the silicate remover.

Hard to say the level before that with only one resin... but I can guess even higher.

Anyway, the ICP test from November (a bit after I added the extra resins) the level dropped to the 31 µg/l...
The silicon level in the tank changed from 276 to 238.

I would assume that if the RO is really the problem, the diatoms should be gone anytime soon... or:
- there is another source for the Silicates
- or it is really not diatoms (No idea what could be, since the tangs and the snails are eating it all day)

I ordered a Silicate test. It will arrive Friday. I’ll share the results right after.

Thanks again!

taricha · Dec 9, 2020

PBar said:
I would assume that if the RO is really the problem, the diatoms should be gone anytime soon... or:
- there is another source for the Silicates
- or it is really not diatoms (No idea what could be, since the tangs and the snails are eating it all day)

Substrate can be a source of silica as mentioned in the article.
There are some media blocks that are made of an Si material (siporax) and have been associated with some high Si readings.
hobby Si kits other than hanna or hach are quite bad at finding Si, even when it's there. just be aware.
but finally, If you aren't constantly adding large amounts of new Si, and what you're growing is getting eaten by herbivores, then it sounds like the issue is going to self-correct in short time.

PBar · Dec 9, 2020

Hi Taricha,
Thanks for the feedback.
Agree with that, if the source (RO) is corrected, should be solved soon.

Thanks for the warning related to the test kids... the only test that I have at home is Hanna KH... hard to trust in the hobby tests.
I sent the water again for an ICP analysis. I want to see again the evolution of Silicon.

By the way, I read the article again and I’m moving back and forth with my opinion

It is a bare bottom tank and I don’t use siporax.
Hard to believe that I still have Diatoms...

In one point, before seen the silicon level in the ICP results, I thought that it was Dinos... specially after seen tiny bubbles in some parts of the rocks by the end of the day.
But the tangs are constantly eating it in the rocks. And as far as I know, nothing eats dinos... so I put that option away.

I’ll try to post a picture while we wait for the results.

PBar · Dec 9, 2020

PBar · Dec 9, 2020

PBar · Dec 9, 2020

Randy Holmes-Farley · Dec 9, 2020

When you clean the glass, is it green or golden brown, when viewed from the side like in the article?

PBar · Dec 9, 2020

Hi Randy,
Lockdown here for a long time already... as such, I’m cleaning the skimmer cup and the glass every night...
I‘ll leave it for a few days now and check it.

PBar · Dec 10, 2020

ok, not the front glass yet but the back part of the tank without cleaning for 3 days.
Seems to be more brown... it is darker, but probably because of the black paint of the back.

PBar · Dec 14, 2020

Hello, just an update:
I received the results from ICP test.
Silicon
RO: 317 µg/l
Tank: 479 µg/l

Both went really up... even worse, I did 2 x 30% water change over the last week... so pretty much feeding my diatoms pets apparently

Mystery... the RO declined the level of Silicon to 30, but now back to 317. Meanwhile I added another resin in the filter.

My next, or last, suspect is the flow in the RO system, which seems to be not very constant...

Dr. Jim · Dec 14, 2020

I use to use Spectrapure's SilicaBuster in my RO/DI. They say it is designed especially for silica but I'm not sure what, if anything, is different or special about it. It always worked nicely for me (although I don't know if I had high silica in the tap water to begin with). Maybe someone else knows if this resin is "superior" for silica?

PBar · Dec 14, 2020

Dear Dr Jim,
thanks for the feedback.
Actually, I ordered this SilicaBuster last week to test. But since I’m in Europe, it will take some extra days to arrive.

My next test now is pass all water again in the 5 DI resins, but really slow and check again the silicates level.
2,5 litres of resin and the rate will be 5 litres per hour.

I also did a hobby test in the water: before the filter, Silicate level is higher than 2 mg/l (max of the test Sera).
After the RO/DI is zero, but hard to believe... after the ICP results.

PBar · Dec 21, 2020

Hello,
as final feedback, seems that the problem is solved.

Apparently, the tap water from my house contains really high silicate levels
I‘m now passing the RO water extremely slowly in the DI resins: 5 litres per hour over (6 resins).

As such, bu just eliminating the silicate in the H2O reservoir, the diatoms are gone completely (two weeks)
Indeed, as Randy mentioned, silica is consumed very fast!

Another interest fact, as it is mentioned in Randy‘s article: after the diatoms were gone, I had for two days a bit cyano - actually just in two tiny spots. Which now are also completely gone.

Once again, thanks for all help and usual support!