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Discussion Starter · #41 ·
Just posted a revision of my Potted Plant article on my website.

In order to revise my Potted Plant Tank article, I tested the effect of an STS gravel layer on the potential removal of added nitrates. I added 10 ppm nitrates to a 20 gal tank with STS (Safe-T-Sorb) and 10 ppm nitrates to a matching 20 gal tank without STS. Goal was to see whether denitrification or nitrification explained the nitrate accumulation I had observed earlier in one of the 10 tanks described in my article. Over a period of 13 days, I measured absolutely no decrease in nitrates in either expt tank. Attached is file describing the expt testing STS's effect on the added nitrates.

Unexpectedly, I ran into a "lurking variable." The guppies in the expt tank without STS were from an older batch that I believe was genetically less "fit" than the batch in the expt tank with STS. Guppy fitness/age may have explained the deaths that occurred during expt, not absence of STS.
 

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Ah, but did the expt tank without STS register a spike in ammonia as happened in your previous nitrate dosage? That was the baffling part (IMO). it was almost as if something was reverse engineering the extra nitrate back into ammonia?

Wait. I guess I should read the article first. :giggle:

EDIT: Never mind. DeadFish= increase in NO3.

Fascinating. So, we're still left with the puzzle of STS somehow increasing nitrification without - seemingly - to increase nitrates. Possible explanations being that plants are perfectly capable of increasing their uptake of nitrates? Potted plants?
 

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Discussion Starter · #43 ·
Please read the article. The subject is complicated and has many variables and blind alleys. Dead fish may have been due to genetic weakness, certainly not nitrates. Nitrates are not toxic. (For a better experiment, I should have used randomly selected individuals in both tanks drawn from one guppy population.) STS is a minor variable that may be irrelevant. However, I believe STS or any baked clay type gravel may be useful, because of clay's known greater nutrient and bacterial binding capacity than sand or gravel or no substrate.

The main take-home message is that good plant growth in 9 out of my 10 tanks removed toxic forms of nitrogen- ammonia and nitrite. I now believe--based on my experiment--that the nitrate accumulation in the outdoor tank was due to nitrification, not denitrification Overall, the article trumpets "Plant Power."
 

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The main take-home message is that good plant growth in 9 out of my 10 tanks removed toxic forms of nitrogen- ammonia and nitrite. I now believe--based on my experiment--that the nitrate accumulation in the outdoor tank was due to nitrification, not denitrification Overall, the article trumpets "Plant Power."
Oops. I just realized i should have said "DeadFish=increase in NH3"
Be that as it may,
i still applaud you for the effort. It's made STS a tad less mysterious and reinforced the primacy of biological processes that are already familiar to hobbyists. For me the take-home message was: every tank is different.
 

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I'm sorry but what is STS ? I really can't keep track of all these abbreviations.
STS= Safe-T-Sorb

To quote from an earlier post:
People have always been attracted to its natural, river bed color - and the fact that it is dirt cheap (no pun intended.) It's amusing to read from the benefit of 20/20 hindsight that everyone's initial desire was to use it as a straight substrate. I think because it looked so natural like soil that they had to be disabused of the notion that it contains any nutrients at all. People also wanted to use it as a cap only to discover that it was lighter and airier than gravel and held plants down only with difficulty.

Only one post mentioned STS in connection with the denitrification process and that was only because of its resemblance to Oil Dri, another tractor supply substance that was being touted as the main medium in a so-called, "anoxic filtration system". But, that's a subject for another thread. What's remarkable here is that STS seems to be creating the conditions for anaerobic bacteria to thrive without actually being anaerobic, at least not in ways that are familiar to any of us who work with dirted tanks.
Some of us theorized that STS might have been initiating some sort of ionization process in the water like some of the commercially available products already on the market, but @dwalstad eliminated that as a possibility fairly early in her speculations.
 

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Discussion Starter · #49 ·
STS, because of its porosity and clay component and high surface area, has plenty of binding sites for nutrients (CEC or 'cation exchange capacity'). It also has plenty of attachment sites for bacteria. If the STS is anaerobic, say at bottom of a deep substrate filled with organic matter, it will support denitrification, an anaerobic process. On the other hand, if the same STS is in an aerobic environment with enough oxygen, it will support aerobic bacteria like nitrifying bacteria. It simply provides attachment sites for bacteria, and since it also binds nutrients (NH4+, K+, etc), it encourages bacterial activity.

Apparently, the thin layer of STS scattered on the bottom of my potted plant tanks stays aerobic, and thus, does not support denitrification. I wasn't sure about this until I did my experiment showing that 10 ppm added nitrates did not decrease over a 13 day period. If tanks were actively denitrifying, I should have measured some decrease in nitrates.

I bought a 40 lb bag of STS for $7 at Tractor Supply Co.
 

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STS, because of its porosity and clay component and high surface area, has plenty of binding sites for nutrients (CEC or 'cation exchange capacity'). It also has plenty of attachment sites for bacteria. If the STS is anaerobic, say at bottom of a deep substrate filled with organic matter, it will support denitrification, an anaerobic process. On the other hand, if the same STS is in an aerobic environment with enough oxygen, it will support aerobic bacteria like nitrifying bacteria. It simply provides attachment sites for bacteria, and since it also binds nutrients (NH4+, K+, etc), it encourages bacterial activity.

Apparently, the thin layer of STS scattered on the bottom of my potted plant tanks stays aerobic, and thus, does not support denitrification. I wasn't sure about this until I did my experiment showing that 10 ppm added nitrates did not decrease over a 13 day period. If tanks were actively denitrifying, I should have measured some decrease in nitrates.

I bought a 40 lb bag of STS for $7 at Tractor Supply Co.
So, it's still conceivable that someone (not saying who necessarily) could concoct the right anaerobic conditions for denitrifying bacteria to thrive by say, stacking a couple of old filter containers filled with STS on top of each other and just letting them sit at the bottom of their tank?
Plant Flowerpot Compost Annual plant Soil
 

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STS, because of its porosity and clay component and high surface area, has plenty of binding sites for nutrients (CEC or 'cation exchange capacity'). It also has plenty of attachment sites for bacteria. If the STS is anaerobic, say at bottom of a deep substrate filled with organic matter, it will support denitrification, an anaerobic process. On the other hand, if the same STS is in an aerobic environment with enough oxygen, it will support aerobic bacteria like nitrifying bacteria. It simply provides attachment sites for bacteria, and since it also binds nutrients (NH4+, K+, etc), it encourages bacterial activity.

Apparently, the thin layer of STS scattered on the bottom of my potted plant tanks stays aerobic, and thus, does not support denitrification. I wasn't sure about this until I did my experiment showing that 10 ppm added nitrates did not decrease over a 13 day period. If tanks were actively denitrifying, I should have measured some decrease in nitrates.

I bought a 40 lb bag of STS for $7 at Tractor Supply Co.
So STS is a geo specific product ? I mean it is more of a brand's name for a product but specific to that brand that may not be available in other geolocation. You describe its behavior but if i were to go to the store it would be next to impossible for me to determine if an alternative product had the right properties ?

Having said this - i have some interest in the topic since I have found that a specific fine inert substrate rapidly produce anaerobic pockets but there is a difference between that type of anaerobic pocket and what you are describing since i find it rapidly kill plants (I've run the experiment several times) - I suspect the difference between this substrate and STS is the clay component allowing for porous property and therefore the anaerobic bacteria you are describing is a bit different. I have another substrate (also inert) that does not have this 'kill plant' property which i have described as porous.

In the first case i am describing above i had a heavily stocked aquarium that I did not perform water changes for 3 months (because it was on the floor and siphoning water out was difficult) but the nitrate level stayed below 2. This was an inert substrate - but instead of releasing sulfur (egg smell) i applied a gentle current over it and it release (I think) nitrogen and very small patches of cyobo developed on it - the positive effect of this gentle current was that the plants grew instead of dying.
 

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So STS is a geo specific product ? I mean it is more of a brand's name for a product but specific to that brand that may not be available in other geolocation. You describe its behavior but if i were to go to the store it would be next to impossible for me to determine if an alternative product had the right properties ?
It's hard to believe there aren't other baked clay products out there with similar properties but under different brand names. It's intended use was (as the brand name implies) for soaking up oil spills in busy truck and long-haul vehicle destinations. Surely, other countries around the world have trucks and surely someone has figured out a way to soak up oil with industrialized clay.

After following @dwalstad's research, my attitude towards STS has changed slightly. I used to think of it as performing some sort of alchemy within the water. But, now I think of it as a kind of super-efficient bio-ring, perhaps 100x more commodious to beneficial bacteria (BB) than anything else aimed at the aquarium market. Based on my own experience - and with the proviso that "every tank is different" - I think you could get away with having a bag of the stuff sitting at the bottom of your aquarium; maybe a more solid container, like a small clay pot, if you are really trying to create anaerobic conditions?
 

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Safe-T-Sorb is calcined (fired or baked) montmorillonite clay:

As mentioned in the article, it is also used as a soil amendment and an ingredient in bonsai soil mix. I use it as an aquarium substrate and in bonsai mix with great results. I've never used it as Diana describes (thin layer over the bottom glass) but most of my tanks have it as a cap over soil. And if I am using a high organic matter or very fertile "soil", I mix the soil half and half with STS. One such tank has been running for over 10 years.

I have been raising platies for a few years, and they are next to impossible to catch in a normal planted tank! The next tank I set up will be potted plants and a thin layer of STS. Thanks again, Diana.
 

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Discussion Starter · #54 ·
STS (Safe-T-Sorb) is a natural clay (montmorillonite of the smectite clay group) mined in western Tennessee (USA). The company's nearby plant heats the clay to 800 degrees F which produces a calcined clay (clay hardened via melting). That temperature results in a material that is partially ceramic. As such it is very absorbent and effective in soaking up liquids, which is its intended purpose. SEACHEM heats their clay from northern Georgia to a higher temperature (1,200 F) from which they get FLUORITE. (Reference: Neil Frank, noted planted tank expert.)

For making pottery, clay is fired/heated to 1,000 to 2,500F. The high temperature melts and hardens the clay particles, somewhat like heating sand to create glass. The clay becomes a ceramic, the hardness depending on the firing temperature.

Kitty litter is only heated to dehydrate (get rid of absorbed water). Dehydration can be done at much lower temperatures (250F? or 150C). Thus, kitty litter has no structure and rapidly breaks down into fine particles (i.e., mud). Mixed with an organic potting soil, kitty litter mud would be highly reactive--release aluminum to create aluminum toxicity?-- whereas any aluminum release from STS gravel would be much more gradual and controlled, such that plant roots could handle it.

Remember that clay is composed of aluminosilicate, meaning that all clays contain aluminum and have the potential to generate aluminum toxicity. In addition, tropical clays may contain iron oxides and aluminum oxides deposited inbetween clay particles. These oxide deposit can cause even more metal toxicity problems. In my book (p. 132) I describe a tank meltdown experience I had from mixing potting soil with just a little bit of laterite clay. It created iron toxicity.

Michael here describes mixing STS with soil. Another knowledgeable hobbyist reported getting good results potting plants in a mixture of STS and soil. STS has a good reputation from experienced hobbyists, including our very own Michael!
 

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Seachem ($35 for a 15lb. bag) gets a lot of mentions on this forum. Has anyone ever tried using it as a bio-filter; perhaps, even as an anaerobic bio-filter?
I've read people putting it in a porous container in a low flow area of the sump for an anaerobic filter. It needs iron to work so an iron-rich material would work.
 

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I've read people putting it in a porous container in a low flow area of the sump for an anaerobic filter. It needs iron to work so an iron-rich material would work.
It's interesting to read the chatter that has accompanied denitrification at various stages of the hobby over the years. If you google Seachem and anaerobic, you see references to Matrix(TM) a volcanic pumice derivative sold at about $16 a pound. It was touted as a more efficient successor to "live rocks" which were actual rocks mined from the ocean floor and popular among saltwater tank enthusiasts for their ability to support colonies of beneficial bacteria. A few years later, the company introduced Denitrate(TM) another gravel-like substance which Seachem straight up touted as being similar to Matrix, (so, Is there much difference between volcanic pumice and calcined clay?) And, judging from the comments on their Amazon pages, users were convinced they had to replace the products every few months as if they were charcoal and would lose their "power" eventually. Curiously, neither product is particularly popular as far as aquarium products go, barely breaking the top 200 "aquarium filter accessories" category in Amazon's Best Seller's Rank.
 

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My biggest concern in this thread is introducing toxicity to the tank. When I read the above past about clay contain aluminium or iron it just makes me thing I should stick to inert substrate. The plants might not grow as well but they grow and the fishes don't have to worry about long term poisoning.

I think the biggest question i have given the above comments on clay is how do you know if any of the products are safe for long term use. I realize this thread doesn't seem to focus on fish health but isn't that a concern when picking your substrates ?
 

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I think the biggest question i have given the above comments on clay is how do you know if any of the products are safe for long term use. I realize this thread doesn't seem to focus on fish health but isn't that a concern when picking your substrates ?
Calcined clay is similar to porcelain and people have been keeping fish in porcelain bowls for a thousand years. I can't speak for the chemical properties of Matrix and Denitrate except to say that Seachem advertises them both as being "inert".
 

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It's interesting to read the chatter that has accompanied denitrification at various stages of the hobby over the years. If you google Seachem and anaerobic, you see references to Matrix(TM) a volcanic pumice derivative sold at about $16 a pound. It was touted as a more efficient successor to "live rocks" which were actual rocks mined from the ocean floor and popular among saltwater tank enthusiasts for their ability to support colonies of beneficial bacteria. A few years later, the company introduced Denitrate(TM) another gravel-like substance which Seachem straight up touted as being similar to Matrix, (so, Is there much difference between volcanic pumice and calcined clay?) And, judging from the comments on their Amazon pages, users were convinced they had to replace the products every few months as if they were charcoal and would lose their "power" eventually. Curiously, neither product is particularly popular as far as aquarium products go, barely breaking the top 200 "aquarium filter accessories" category in Amazon's Best Seller's Rank.
I bet we can buy pumice or even perlite and put them in mesh bags, it would be a lot cheaper. Their pores are bigger than the baked red clay but they don't have the iron needed in the denitrification process. The pores do eventually get clogged up with biomatter but that's simply solved by baking or bleaching the organics away. Maybe a mix of pumice and baked red clay would work best. Since we're in the plant hobby, we need nitrogen for the plants so we don't need this setup.
 
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