Please help : Silicates and Diatoms

[BubblesandSqueak]

So I can’t find my kids scope and hoping my wife knows where it is. Test kits arrive Monday. Lights still off but I can see the brownish tinge to the water now and the brown on the sand is darker. Will it make it worse to stir it up to try and run through the filter socks? Should I do another water change or leave be? I’d run down and get RO from Wjole Foods like I previously was and had no issues. Or I could buy the NutriSea Water from LFS?
Was looking at the BRS upgrade kit to make this 6 stage and of course they are out of stock.

 

[Ziggy17]

I wouldn’t try to solve a problem that doesn’t exist yet. Meaning, extra Di stages for RODI. It could be dinos, and if it is, all the extra Di stages won’t help. The brown dust “likely being diatoms” is a fallacy. Many of us who have had Dinos started off as a light brown dusting. And we all took advice based on said fallacy, and left it alone to go away. only to find out that it was dinos, and instead of eradicating the Dino’s early and making the job easier, we had dinos that had really dug in and took far longer to get rid of. Do you have a LFS that you can borrow a microscope from? That’s what I did as mine took a few weeks to get here from Amazon.

Step one is Find out what you have. If it’s Si, then chase the culprit and take steps. If it’s dinos , plan the eradication method. I wouldn’t do anything until you know. Or else it’s throwing good money at bad money.

 

[BubblesandSqueak]

Well I stirred the sand and let it collect in the socks. I’ll change the socks in the morning and see what happens. Added the extra CUC too. Picked up 20 gallons of the previous RO I was using in case I get a spike and need to change before the silica kit comes.

 

[BubblesandSqueak]

So the colors are kind of hard to distinguish. What am I looking at here? I think it’s normal.
The 6 cup tray is left to right normal range: source water, biocube 32, IM112, square cuvet is low range IM112 and the single one in the tray is the normal range control.

 

[BubblesandSqueak]

bump

 

[Randy Holmes-Farley]

Any insight on why the filtered water pH would increase from 7.01 to 8.69?

Assuming you mean an RO/DI, then:

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com

Final Effluent pH

Aside from the issues discussed above concerning the effluent’s pH when the DI resin becomes depleted, the final pH coming out of an RO/DI system should not significantly concern reef aquarists. Many aquarists with low pH problems have asked, for example, if their aquarium’s low pH may be caused by their replacing evaporated water with RO/DI water that they measure to have a pH below 7. In short, the answer is no, this is not a cause of low pH nor is it something to be generally concerned about, for the following reasons:

1. The pH of totally pure water is around 7 (with the exact value depending on temperature). As carbon dioxide from the atmosphere enters the water, the pH drops into the 6’s and even into the 5’s, depending on the amount of CO2. At saturation with the level of CO2 in normal (outside) air, the pH would be about 5.66. Indoor air often has even more CO2, and the pH can drop a bit lower, into the 5’s. Consequently, the pH of highly purified water coming from an RO/DI unit is expected to be in the pH 5-7 range.

2. The pH of highly purified water is not accurately measured by test kits, or by pH meters. There are several different reasons for this, including the fact that highly purified water has very little buffering capacity, so its pH is easily changed. Even the acidity or basicity of a pH test kit’s indicator dye is enough to alter pure water’s measured pH. As for pH meters, the probes themselves do not function well in the very low ionic strength of pure freshwater, and trace impurities on them can swing the pH around quite a bit.

3. The pH of the combination of two solutions does not necessarily reflect the average (not even a weighted average) of their two pH values. The final pH of a mixture may actually not even be between the pH’s of the two solutions when combined. Consequently, adding pH 7 pure water to pH 8.2 seawater may not even result in a pH below 8.2, but rather might be higher than 8.2 (for complex reasons relating to the acidity of bicarbonate in seawater vs. freshwater).

 

[Randy Holmes-Farley]

If there is too much silicate in the DI effluent (some is OK, a lot may not be), then using a second DI after the first one will help. Be sure to monitor the TDS between the two and replace the first one as soon as TDS rises at all.

Some companies claim to be DI resins that are better at binding silicate, but I've not seen any data to support that claim.

 

[BubblesandSqueak]

Assuming you mean an RO/DI, then:

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com

Final Effluent pH

Aside from the issues discussed above concerning the effluent’s pH when the DI resin becomes depleted, the final pH coming out of an RO/DI system should not significantly concern reef aquarists. Many aquarists with low pH problems have asked, for example, if their aquarium’s low pH may be caused by their replacing evaporated water with RO/DI water that they measure to have a pH below 7. In short, the answer is no, this is not a cause of low pH nor is it something to be generally concerned about, for the following reasons:

1. The pH of totally pure water is around 7 (with the exact value depending on temperature). As carbon dioxide from the atmosphere enters the water, the pH drops into the 6’s and even into the 5’s, depending on the amount of CO2. At saturation with the level of CO2 in normal (outside) air, the pH would be about 5.66. Indoor air often has even more CO2, and the pH can drop a bit lower, into the 5’s. Consequently, the pH of highly purified water coming from an RO/DI unit is expected to be in the pH 5-7 range.

2. The pH of highly purified water is not accurately measured by test kits, or by pH meters. There are several different reasons for this, including the fact that highly purified water has very little buffering capacity, so its pH is easily changed. Even the acidity or basicity of a pH test kit’s indicator dye is enough to alter pure water’s measured pH. As for pH meters, the probes themselves do not function well in the very low ionic strength of pure freshwater, and trace impurities on them can swing the pH around quite a bit.

3. The pH of the combination of two solutions does not necessarily reflect the average (not even a weighted average) of their two pH values. The final pH of a mixture may actually not even be between the pH’s of the two solutions when combined. Consequently, adding pH 7 pure water to pH 8.2 seawater may not even result in a pH below 8.2, but rather might be higher than 8.2 (for complex reasons relating to the acidity of bicarbonate in seawater vs. freshwater).

thank you. this explains a lot.

 

[BubblesandSqueak]

If there is too much silicate in the DI effluent (some is OK, a lot may not be), then using a second DI after the first one will help. Be sure to monitor the TDS between the two and replace the first one as soon as TDS rises at all.

Some companies claim to be DI resins that are better at binding silicate, but I've not seen any data to support that claim.

are my results high though? it doesn't seem like it. as I was searching through info, I even found something that said inadequate lighting could produce a diatom bloom and to increase the intensity. I chose lights out which I will start ramping up the light again. if my results are not bad, then the only thing I'm wondering if there was a lot of silica in the sand still that got stirred up, then bloom, then now the silica is being used up so back to normal? so next stir/vacuum it may repeat.

 

[Randy Holmes-Farley]

I cannot see how inadequate lighting promotes a diatom bloom.

I could not really assess your pictures. How much do you think is in the ro/di effluent?

 

[BubblesandSqueak]

I cannot see how inadequate lighting promotes a diatom bloom.

I could not really assess your pictures. How much do you think is in the ro/di effluent?

The reference test for the control says it’s supposed to be 6mg/L. Natural sea water supposed to be 10mg/L. I believe my tank is 2mg/L. I did see I messed up the low range but normal range looks to be OK. I’ll repeat the low range as a reference to myself but doubt I will see the color.

 

[BubblesandSqueak]

I cannot see how inadequate lighting promotes a diatom bloom.

This was one of the articles. Brown outcompetes green in low light.

Brown Algae (Diatoms): Causes, Prevention, and Treatment

Brown algae (diatoms), forming soft clumps on aquarium surfaces, indicate poor water conditions & arise from excess nutrients & silicates.

oakharts.com

 

[Randy Holmes-Farley]

The reference test for the control says it’s supposed to be 6mg/L. Natural sea water supposed to be 10mg/L. I believe my tank is 2mg/L. I did see I messed up the low range but normal range looks to be OK. I’ll repeat the low range as a reference to myself but doubt I will see the color.

Those supposed to be numbers are not reasonable. Seawater is not 10 mg/L. Even 2 mg/L is high for surface seawater. It is typically well below 1 ppm.

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

When I dosed silicate, I targeted dosing about 1 ppm, which is typically rapidly depleted.

In any case, it’s the silica in the ro/di I was asking about.

 

[Randy Holmes-Farley]

This was one of the articles. Brown outcompetes green in low light.

Brown Algae (Diatoms): Causes, Prevention, and Treatment

Brown algae (diatoms), forming soft clumps on aquarium surfaces, indicate poor water conditions & arise from excess nutrients & silicates.

oakharts.com

I’d ignore that article. I do not know if it is correct or not for the freshwater scenarios it refers to, but it is talking about green algae out competing the diatoms when there is plenty of silicate, and that clearly happens in reef tanks at all light levels. I’ve demonstrated it in my tank. Dose silicate and the growths on the glass, even in bright light turn from green to golden brown.

In your case, the brown growth is at least partly in sand, where presumably green algae is not what you want to replace the diatoms anyway.

Restricting silicate is the way to beat diatoms in a reef tank, not brighter light.

 

[Ziggy17]

What test kit did you use? The only two samples you need to look at is the Rodi sample and a tank sample. Do them separately and post the results in a separate post. That way it’s easy to read and understand for readers.

when you start researching what a two stage Di resin you will realize that it just helps reduce the cost of Di resin, as you buy and use two types, Anion and Cation. Anion is responsible for silicates PO4 and NO3 filtration. So it depletes caster that the Cation, which filters calcium, copper iron etc… the Anion depletes faster, so a two stage lets you just replace that and keep the cation going longer, saving you money long term. Running 2 stages of the all in one Di resin doesn’t give you better protection, it will just last a little longer before changing out the AIO resin. If the Anion resin is charged, it’s not going to let Si sneak through. That’s why they make the colour changing, if it’s blue, it’s charged, and working. If it’s brown, it’s no longer charged and leaches back.

If I’m wrong, some one please let me know. I’m not a chemist .

 

[Randy Holmes-Farley]

I personally wasn’t recommending separate anion and cation, but two mixed beds. That way there are two chances to catch silicate.

 

[killer2001]

I noticed diatom production starts to fall off once silicon values were < 0.6ppm. So targeting about 0.6 to 1.0ppm in my tank has kept things running smoothly.

 

[Ziggy17]

I personally wasn’t recommending separate anion and cation, but two mixed beds. That way there are two chances to catch silicate.

Understood. Will the first stage of mixed Di not attract all Si if the bed is charged? If not, what would the mechanism be to allow the Si to get past a full stage of charged Anion in the first cylinder but be caught in the second? I’m curious to learn as I’ve only done some light ish reading on it in the past, and I heavily rely on expert opinions like yourself for this stuff.

 

[Randy Holmes-Farley]

Understood. Will the first stage of mixed Di not attract all Si if the bed is charged? If not, what would the mechanism be to allow the Si to get past a full stage of charged Anion in the first cylinder but be caught in the second? I’m curious to learn as I’ve only done some light ish reading on it in the past, and I heavily rely on expert opinions like yourself for this stuff.

Silica gets through the ro membrane as silicic acid, and is among the more weakly bound ions as silicate in a di, so typically small amounts get through.

This article should explain these issues in depth:

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com

 

[Ziggy17]

Silica gets through the ro membrane as silicic acid, and is among the more weakly bound ions as silicate in a di, so typically small amounts get through.

This article should explain these issues in depth:

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com

Yes I’ve read that, thank you. It doesn’t explain why Si would not be caught in the first cylinder, but caught in the second. If the ion is charged, it will be caught in that first stage by the Anion. If it’s not charged, it passes through, regardless of how many stages are in place. What would cause a lesser ionic bond that the Si ion passes through the first but not the second? What changes happen between the stages that helps make this correction? Does the Si gets “bumped out” by a stronger ionic bond, ie PO4? If so, how does that happen? And what gets priority if it’s not FCFS. That’s what I’m most curious about.

I’m not challenging the findings, just digging deeper for the complete answer. It’s how I learn.