NEVER ENDING DIATOM BATTLE!

[Flippers4pups]

I've been battling diatoms for several years now. Yes, it's diatoms and nothing else. It hasn't effected any corals and isn't present on glass or rock. Tank was started in 2015.

Sand bed is the most effected. Last year I replaced my sand bed with new Caribsea aragonite special grade thinking the sand I started with was contaminated possibly with silicate. This sand replacement had no effect on the diatom problem. Sand bed has been vacuumed at times with no effect on the diatoms. Stays consistent.

Source water is from a 6 stage RO/DI unit. Membrane is about three years old. I replace all filters every 6 months. Unit has two mix bed DI resin chambers. TDS is always 0.

Possible sources of silicate/silicon contamination are from the following:

Source water

Calcium hydroxide (Kalkwasser)

Rock (dry rock)

Those are my theories behind the source as Ive not tested my source water or my ATO reservoir water.

Observations:

I do a weekly water change of 10 gallons. After the water change the diatoms increase and decrease a little at the end of the week.

If I go two weeks without a water change, they subside more, but are still present.

Lights out for four days diminishes them a little, but return.

ATO reservoir top off is every week of ten gallons

All of this leads me to believe there's a elevated of silicate/silicon in the water coming into the system.

Ideas or personal experience in combating and overcoming this issue is much appreciated from the community!

 

[Sallstrom]

Since we’ve sending water samples to Triton lab since 2014, I know what levels we’ve had in our tanks at work. Some 10x the recommended value, most times just slightly above. I haven’t seen any difference in diatoms though. So I don’t believe that’s the cause.

I do believe diatoms are great opportunists and they are often the first organisms to start establishing on new and clean surfaces. So in your case, the sand grains are clean and gets light on them. Diatoms start to grow. You clean the sand, new clean sand grains get light on them, new diatoms.

I guess you need a really good sand cleaning crew if you want a white sand bed in a tank with lights enough for corals. Perhaps it could work with sea cucumbers and sand shifting sea stars. Or a fish filtering the sand.

Or wait until coralline algae covering the sand grains and outcompetes the diatoms.

Just some ideas and guesses

 

[Randy Holmes-Farley Verified Community Expert]

Have you measured silicate? (note there are some concerns about the Salifert kit reliability)

Silicate can be bound by GFO. If phosphate is a concern, using GFO intermittently and dosing phosphate (if it gets low) might be an option if you cannot find a definitive source of silicate.

 

[Randy Holmes-Farley Verified Community Expert]

Since we’ve sending water samples to Triton lab since 2014, I know what levels we’ve had in our tanks at work. Some 10x the recommended value, most times just slightly above. I haven’t seen any difference in diatoms though. So I don’t believe that’s the cause.

Silicate is absolutely required for diatoms and reducing it will eliminate them as a problem. Adding silicate often increases diatoms (it clearly did in my tank each time I dosed it).

That doesn't mean that even if there is plenty of silicate, that they will dominate other organisms that are all competing for other chemicals, space, etc.

 

[Sallstrom]

Silicate is absolutely required for diatoms and reducing it will eliminate them as a problem. Adding silicate often increases diatoms (it clearly did in my tank each time I dosed it).

That doesn't mean that even if there is plenty of silicate, that they will dominate other organisms that are all competing for other chemicals, space, etc.

My point, which you didn’t include in the quote, was that diatoms need free space. They won’t outcompete more hardy organisms like coralline algae or corals IMO. And they are fast growers when new free space emerges.

Everytime, at least when I’ve done it, diatoms are the first to establish when adding something new to an already mature reef tank. Like a dry and clean rock.
But I’ve never tried that in a tank without silica in the water

The value Triton recommends for Si is 100ug/l. What level would you recommend for “eliminate them as a problem”?

 

[Randy Holmes-Farley Verified Community Expert]

I agree on the place to grow issue, and I mentioned it in my post. Every time I dosed silicate When I hadn’t for a while, the new growth in the glass was golden brown instead of green. I didn’t have any diatom “problem”.

I do not recall the exact silicate level to restrict diatom growth, and I’m not sure a Triton test is always a good indicator since there are other forms of silicon than silicate.

 

[Randy Holmes-Farley Verified Community Expert]

The value Triton recommends for Si is 100ug/l. What level would you recommend for “eliminate them as a problem”?

Triton testing issue aside, this is from one of my articles:

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

With one exception (discussed below) all diatoms require silica for growth, and low silica levels cause significant changes in the cell cycle.7 Silicon is a major limiting nutrient for diatom growth in certain parts of the oceans,8 although iron,9 nitrogen, and phosphorus can also be limiting. There have been many studies on the uptake of silica by diatoms. Most diatoms take up silica in the form of silicic acid, although one has been shown to take up the silicate form.10 If absorbing silica is a limiting factor, then it makes sense to transport silicic acid since it is present at much higher concentrations than is silicate, and hence is potentially easier to transport.

Different diatom species have different abilities to absorb silica from the water. That is, as the silica concentration drops, some diatoms can continue to pull silica from the water while others cannot. Most diatoms have half maximal rates of silica absorption of 0.7-10 uM 0.04 – 0.6 ppm SiO2), but some are substantially higher, up to about 60 uM (2.6 ppm SiO2). The in-situ average for biogenic silica uptake in the surface layer of the equatorial pacific showed half maximal uptake at a silica concentration of 1.6 uM at 3°S and 2.4 uM at the equator, which was close to the silica concentrations present.

There apparently are genes for many different silica transporters in each of the diatom species that has been investigated.8 Diatoms also somehow maintain internal silicic acid concentrations at levels higher than its solubility, but the mechanism for accomplishing this is unclear. Nevertheless, it is obvious that this facilitates the deposition process, and inhibits dissolution of the existing frustule. Diatoms apparently use proteins to guide the deposition process, where soluble silica is converted into the intricate solid frustule, but exactly how this role is accomplished is not known.8

In a reef tank like mine with silica concentrations below 0.8 uM (0.05 ppm SiO2, the practical limit of the Hach silica kit), some diatoms will have a hard time absorbing silica. Many reef tanks may, in fact, be selecting for diatoms that are able to get enough silica at the low concentrations typically available. Are diatoms silica-limited in reef tanks? That question is addressed experimentally below.

In the oceans, diatoms are silica limited in some natural settings (like the polar regions and the Sargasso Sea, where the ambient silica concentration is less than 1 uM (0.06 ppm SiO2).11 There have also been many cases where eutrophication of natural waters has raised nitrogen and phosphorus levels to the point where silica has become limiting,12 even when it was not limiting in pristine waters. In reef tanks, where nitrogen and phosphorus are often not in short supply, it makes sense that silica could be limiting. In case you were thinking that silica limitation to diatom growth is necessarily a good thing, there are drawbacks. The limitation of silica, inhibiting the growth of diatoms that would otherwise take up the limiting nutrients nitrogen and phosphorus, has even been implicated in blooms of cyanobacteria.1

 

[ScottR]

PhosGuard by seachem apparently removes silicates. I don’t find diatoms to be a problem usually so never tried this as a method of removal.

 

[Phillthy]

What about adding a chaeto chamber? Uv light?

 

[serwobow]

A diatom issue in an established tank sounds strange to me, since I dont have any diatoms and have been dosing about 50ug/L of silica every day to my tank for years (my top off water (tap water) is loaded with silica (3000ug/L)). I think Randy posted an article about his dosing of silicates a long time ago, and found that it is rapidly depleted from the aquarium. That has certainly been my experience, as my tank level is steady and only slightly elevated at 150ug/L. I think a lot of things must eat diatoms or outcompete them. I remember that my snails and algae blenny enjoyed eating them. Sorry to doubt your diagnosis, but is there a chance you have dinos rather than diatoms? They look similar from a distance.

 

[Heart of Dixie]

Are your mixed bed DI cartridges the blue kind? If so, I think the blue change color with the cation (positive charged particles). Silicate is negative charged and will not change the color. Your anion resin may be loaded and silicates are going thru. Try the purple mixed resin that changes with the negative ions. For the same reason as you are having I switched to 3 di cartridges: first one is pure cation +, the second anion -, the third purple mixed bed. There is a video on BRS TV about this set-up. I hope you win the battle. Now if we could just figure out how to safely and easily kill vermetid snails.

 

[Randy Holmes-Farley Verified Community Expert]

I'd suggest not going by color change at all, and change DI based on rising from 0 to 1 ppm TDS.

 

[Flippers4pups]

Here's the never ending battle:

I am ordering a Hanna HI 705 to test for silica. It's a low range checker.

I have contemplated buying some Anion color changing resin. But in the interim Ive dumped my first mixed bed resin chamber and exchanged it for the last mixed bed resin. The first was 3/4 depleted, the last was full.

So now I've got a full bed mix resin with the TDS meter and lastly the chamber with GFO. This is a attempt to insure removal of any potential silica getting past the RO/DI unit. Once I have the Checker I can confirm what's going on.

 

[KJoFan]

I have the same/similar problem in my system. 2+ years old and on going diatoms. Last ATI ICP test indicated silicon in my RO/DI water. I switched to the 3 stage DI system from BRS awhile ago. My Cation resin seems to never exhaust (based on color change) while my anion resin gets killed fast. my current canister shows 3/4 depleted after about 100g of finished product water. Even though it's only showing 3/4 color change I'm thinking it's exhausted before that. I do have the mixed bed as the 3rd stage which does not show depletion based on color AND TDS meter shows 0 after that final stage. But, none the less silicon is present and elevated in display tank.

I have no idea how to rectify this other than blowing through anion resin at a ridiculous rate which I don't want to do. I am considering just employing something like Phosguard to help, but I don't know if that's a solid choice or not.

I also considered trying the Spectrapure Maxcap Silica buster cartridges to see if they made any difference, but haven't done it.

In fact, I am tearing down my 150g and 60g frag tank to reduce down to a single 50g tank partly because the cost of producing so much water/using so much DI resin and STILL having a subpar product as a result is disheartening.

I am following though to see if there's a solution to this for my new tank. I also thought a smaller tank would be easier to employ things like Phosguard to help battle this problem.

 

[Flippers4pups]

I have the same/similar problem in my system. 2+ years old and on going diatoms. Last ATI ICP test indicated silicon in my RO/DI water. I switched to the 3 stage DI system from BRS awhile ago. My Cation resin seems to never exhaust (based on color change) while my anion resin gets killed fast. my current canister shows 3/4 depleted after about 100g of finished product water. Even though it's only showing 3/4 color change I'm thinking it's exhausted before that. I do have the mixed bed as the 3rd stage which does not show depletion based on color AND TDS meter shows 0 after that final stage. But, none the less silicon is present and elevated in display tank.

I have no idea how to rectify this other than blowing through anion resin at a ridiculous rate which I don't want to do. I am considering just employing something like Phosguard to help, but I don't know if that's a solid choice or not.

I also considered trying the Spectrapure Maxcap Silica buster cartridges to see if they made any difference, but haven't done it.

In fact, I am tearing down my 150g and 60g frag tank to reduce down to a single 50g tank partly because the cost of producing so much water/using so much DI resin and STILL having a subpar product as a result is disheartening.

I am following though to see if there's a solution to this for my new tank. I also thought a smaller tank would be easier to employ things like Phosguard to help battle this problem.

One of the reasons I'm trying GFO down stream. I've heard Anion alone can be depleted extremely quickly. Hopefully the GFO will last a great deal of time.

 

[KJoFan]

One of the reasons I'm trying GFO down stream. I've heard Anion alone can be depleted extremely quickly. Hopefully the GFO will last a great deal of time.

You are implementing gfo as part of your RO/DI system, am I getting that correctly?

 

[Miller535]

I have the same/similar problem in my system. 2+ years old and on going diatoms. Last ATI ICP test indicated silicon in my RO/DI water. I switched to the 3 stage DI system from BRS awhile ago. My Cation resin seems to never exhaust (based on color change) while my anion resin gets killed fast. my current canister shows 3/4 depleted after about 100g of finished product water. Even though it's only showing 3/4 color change I'm thinking it's exhausted before that. I do have the mixed bed as the 3rd stage which does not show depletion based on color AND TDS meter shows 0 after that final stage. But, none the less silicon is present and elevated in display tank.

I have no idea how to rectify this other than blowing through anion resin at a ridiculous rate which I don't want to do. I am considering just employing something like Phosguard to help, but I don't know if that's a solid choice or not.

I also considered trying the Spectrapure Maxcap Silica buster cartridges to see if they made any difference, but haven't done it.

In fact, I am tearing down my 150g and 60g frag tank to reduce down to a single 50g tank partly because the cost of producing so much water/using so much DI resin and STILL having a subpar product as a result is disheartening.

I am following though to see if there's a solution to this for my new tank. I also thought a smaller tank would be easier to employ things like Phosguard to help battle this problem.

As Randy said earlier, you could always periodically use GFO and then dose Phosphate as needed. I have dosed Neophos, and it would be much cheaper to dose that, then keep blowing through DI.

At how good GFO is at silicates, I can tell you this. One month I did a Triton test and had a SI level of 1,000, put GFO in and it dropped to like 100, just 4 or 5 weeks later.

 

[november290]

Totally against a bare bottom tank? You could just eliminate the sand, that seems to be the breeding ground. Realize that may not be the answer you are looking for but it’s an answer!

 

[Flippers4pups]

You are implementing gfo as part of your RO/DI system, am I getting that correctly?

Yes.

 

[Flippers4pups]

Totally against a bare bottom tank? You could just eliminate the sand, that seems to be the breeding ground. Realize that may not be the answer you are looking for but it’s an answer!

Wrasses. No go.