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Discussion Starter · #1 ·
Dirt Lovers! I obtained some useful info on STS (Safe T Sorb) during a Nano Tank aquascaping demonstration by the noted aquarist Mark Denaro (author of The 101 Best Freshwater Nano Species). Demo was sponsored by the Raleigh Aquarium Society (RAS).

Mr. Denaro used STS as the substrate (2 Photos). Attractive product, inexpensive, and used for years by Aquatic Gardeners Association. 40 lb bags sell at Tractor Supply stores for about $7. Apparently, STS works well for large High Tech tanks with artificial CO2 injection and fertilizers.

For an NPT, I would not substitute it 100% for soil; it doesn't have any organic matter or major nutrients to get plants off to a good start in a new setup.

HOWEVER, STS might make an excellent cover/cap for a soil substrate. I've always used gravel or sand, but I think that STS might be better. Here's why. Unlike gravel, it will "capture and bind" nutrients released by the soil substrate in a new setup. The release of excess nutrients into the water is often a problem with fertile soil substrates. Fresh STS would act like a nutrient sponge in a new setup. Long term, the STS along with the soil, would serve as a reservoir of nutrients for rooted plants.

STS is special. It is a montmorillonite clay heated to about 800F. This moderate heating partially solidifies the natural clay particles, changing them to a firmer, more glass-like material. Clay is converted to pottery, usually with much higher temperatures (~1800F?), while kitty litter is heated (300 F?) only to dry out the clay. Apparently, the STS breaks down a little over time but nothing like kitty litter, which eventually forms a gummy mess.

For a comparison of gravel versus STS as a soil cap, I set up two 2 gal tanks with an organic potting soil underlayer. I capped the soil in one tank with gravel as usual; the other with STS. I planted Sagittaria graminea and S. subulata in each and changed water twice in both tanks (Photo). The next day, the STS tank's water still had some turbidity, but most was gone the next day.

On the third day (Photo), the gravel cap tank had orange/brown-tinted water, which is pretty typical. (An organic soil often releases humic acids.) What was amazing, though, is that the STS tank did not show this tinted water! My soil textbook describes the absorption of humic acids by clay particles.

On fourth day, I changed the water and both tanks looked decent (Photo)

Also, the pH was neutral in the STS tank and high (~8.2) in the gravel tank. This reflects the STS absorption of bicarbonates, which could bring down the KH. (STS is known to sometimes reduce the KH.)

I measured and found no ammonia in either tank. (I may have to repeat experiment using a more fertilized soil.)

I think the STS cap would counteract the occasional, temporary release of excess nutrients and humic acids from some soils. Plus it looks nice and is inexpensive!
 

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I love this stuff and use it as a cap in almost all my tanks. Also, if the soil substrate is highly organic (as is the case with most commercial potting mixes) I mix STS half and half with the potting mix for all the reasons that make it a good cap.
 

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Discussion Starter · #4 ·
Racoons got into the tanks two days ago and ended my experiment. Alas, I took photo today of the aftermath and after removing some plants. It shows the greater tea-color from humus in the tank with gravel (tank on right). Note how the tank on the left with STS has much less humus color.

Clay is negatively charged and so is humus. They should repel each other. How then does clay bind humus? The answer is “cation bridges.” My soil textbook* shows the binding of humus to clay via cation bridges. That is, clay binds cations shown in the figure as metals (Al+++, Fe+++, Ca++, Mg++, etc); humus in turn binds to the cations. Sometimes, this binding includes water, as shown in Fig 18.6b. The textbook makes a point that Na+, with only one positive charge, will NOT serve as cation bridge.

* Wild, Alan. 1988. Russell's Soil Conditions and Plant Growth (11th Edition). John Wiley & Sons (NY), 991 pp. Figure is from p. 582.
 

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This is really an amazing new proven informations. I recently set up a walstad bowl, even with just kitty litter mixed with my potting soil, I can right away see the advantage of having clay. Not too much of those tannin colors. And I think I’m getting very less algae this way compared to my previous set up without clay.
 

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Discussion Starter · #7 ·
This is really an amazing new proven informations. I recently set up a walstad bowl, even with just kitty litter mixed with my potting soil, I can right away see the advantage of having clay. Not too much of those tannin colors. And I think I'm getting very less algae this way compared to my previous set up without clay.
Very interesting and thank you for writing. I honestly had not realized the value of clay, in whatever its forms. I may add a small revision in next printing (#12) of my book about this! Granted, I've been a little slow to pick up on this. It was only the STS results--very stunning-- that sent me back to my soil textbook.

BTW, the STS used for the August RAS (Raleigh Aquarium Society) demo was provided by Neil Frank, previous editor of 'The Aquatic Gardener'. Neil is now using STS in his tanks. It was his idea for Mark Denaro to use the STS for his aquascaping demo.
 

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Thank you Ms. Diana. I wouldn’t be confident to set up my bowl without Sir Michaels help. Clay mixed with the soil is so far showing me really better results. Though knowing that the cat litter will turn into a mud. I put the clay first as first layer (tiny amount) then soil on top, and lastly the 2-3mm natural gravels. I’m sure cat litter mud would suffocate the soil over time if i put it above the soil.

By any chance you’re gonna come up with a new revised book about ecology of planted aquarium Ms. Diana?
 

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Discussion Starter · #9 ·
Thank you Ms. Diana. I wouldn't be confident to set up my bowl without Sir Michaels help. Clay mixed with the soil is so far showing me really better results. Though knowing that the cat litter will turn into a mud. I put the clay first as first layer (tiny amount) then soil on top, and lastly the 2-3mm natural gravels. I'm sure cat litter mud would suffocate the soil over time if i put it above the soil.

By any chance you're gonna come up with a new revised book about ecology of planted aquarium Ms. Diana?
You seem pretty savy on this kitty litter business, such as not putting it on top of soil. I plan to try a few experiments with kitty litter and STS. It seems I was too fast to condemn clay in general based on dismal results with a commercial clay product (Dupla's laterite).

I don't plan to prepare a revised edition of Ecology of the Planted Aquarium until or unless it needs to be revised. I don't see that much has changed. A new edition would be mostly cosmetic and to slap on a newer publication date so that book doesn't look "dated."

For the clay-humus binding business, what I'll probably do--as I've done in the past--, is add "replacement pages" with the next printing. I will make sure that the eBook gets updated as well.
 

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Discussion Starter · #10 · (Edited)
I was getting ready to tear down the two experimental tanks when I realized that it would be easier just to reset the tanks up and "soldier on." I will continue to follow tanks for next precious weeks of summer to see if there is any effect of STS on plant growth.

More importantly, I realized that I was falling into the beginner trap of expecting only perfection with no setup problems.

Thus, I removed most of water yesterday, replanted with S. graminea, S. subulata, and a sprig of H. difformis (submersed form). Yes, the soil was disturbed and lying on surface, but so what? (If the tank ends up like Mysiak's, it won't matter.) I added small stones to hold plants down and a 1/4 cup more of soil covering. Then, I changed water twice.

Photo shows tanks after their new makeover. Tanks will now get enhanced night-time security!
 

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Discussion Starter · #11 · (Edited)
I have some interesting results from my bottle jar experiments that have made me think twice--and thrice-- about recommending STS. Unexpected results!

This bottle test experiment was designed to show that an STS cap would capture ammonia in the water and the soil. So I soaked the STS/soil in a liquid fertilizer solution containing 15 ppm ammonia for a few minutes. Then, I changed water to remove the ammonia for my start on 8/22 (Photo). Two days later on 8/24, I measured notably less NH3 in jars with STS, just like I had hoped and predicted.

However, at about 12 days, the NH3 increased dramatically in STS jars to 5 ppm. The two sand jars showed no ammonia. I think the STS acidity created a "soil meltdown." Dying soil bacteria and other microbes released their ammonia into the water.

Granted, my bottle tests don't reflect the tank situation where there's more oxygen and a greater volume of water over the STS. Some people treat the STS beforehand with baking soda. Probably not a bad idea. I have a feeling that neutralizing the acidity of the STS beforehand would have prevented the soil meltdown, but that's another experiment. :)

Attached are pictures of the bottles and my measurements of the water.

Bottom Line: Be careful using STS as a soil cover!! Gravel and sand are safer, less complicated.
 

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Thanks for the head's up! I was just planning on a trip to buy some STS at Tractor Supply, about 2 blocks from me. I may decide to go back to either pool filter sand or Black Beauty blasting grit. (My tank is down now, waiting for a move in a couple of months, and restarting the tank)
 

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Discussion Starter · #14 ·
My tapwater is moderately hard. GH = 9 and KH = 7. My concern is that people with softwater may cover soil with an inch or more of STS, totally oblivious to the fact that a large volume of STS will generate acidity. With experienced aquarists like yourself, STS presents no problem and can be advantageous.

That said, I still have 2 more experiments, ones that deal with plant growth. Will post the results within next month.

Also, I've started scattering small amounts of STS to create a thin layer in a guppy breeding tank with potted plants. Will monitor pH, but I think the STS will work just fine, better than the bare glass bottom that I previously had.

Until my stash of cheap STS runs out, I'll continue to play with it. :)
 

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My tapwater is moderately hard. GH = 9 and KH = 7. My concern is that people with softwater may cover soil with an inch or more of STS, totally oblivious to the fact that a large volume of STS will generate acidity. With experienced aquarists like yourself, STS presents no problem and can be advantageous.

That said, I still have 2 more experiments, ones that deal with plant growth. Will post the results within next month.

Also, I've started scattering small amounts of STS to create a thin layer in a guppy breeding tank with potted plants. Will monitor pH, but I think the STS will work just fine, better than the bare glass bottom that I previously had.

Until my stash of cheap STS runs out, I'll continue to play with it. :)
My last set-up cost me $55 for substrate. This one will be less than $20. El Natural is also El Cheapo!!
 

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For those interested in using safe-T-sorb. Use clarifier and fine filter floss when first starting the tank up. This stuff has a lot of dust and will take several days to clear up and about a week to reach near perfect clarity if using a large canister filter. As soon as you disturb it there will be a cloud of fine silt released. Only takes a few hours to clear up after replanting a few things. STS is also very light and difficult to plant stem plants at first. There's a lot of air trapped inside each piece of substrate and will take a few weeks to remove all of it. After a year or two, it all becomes very soft and easy to break into mud with the slightest pinch. Will need to be replaced yearly for the average person that likes to plant and rearrange things.

I suggest 1/2" to 1" of topsoil with osmocote fertilizer mixed in. Then cover with fiberglass screen material. Several rocks along the outer edges of the screen to hold it down. Then cap it with 2" to 4" of STS. The screen material prevents the topsoil from breaking out when a plant is uprooted. Allows plants to be disturbed more often without releasing too much nutrients into the water column and cause an algae outbreak. I also use a thin layer of heavier planting substrate to cap the STS. Makes it easier to plant stem plants or any buoyant pearling plants from floating up. After a few months the STS becomes heavier and easier to plant into.
 

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For those interested in using safe-T-sorb. Use clarifier and fine filter floss when first starting the tank up. This stuff has a lot of dust and will take several days to clear up and about a week to reach near perfect clarity if using a large canister filter. As soon as you disturb it there will be a cloud of fine silt released. Only takes a few hours to clear up after replanting a few things. STS is also very light and difficult to plant stem plants at first. There's a lot of air trapped inside each piece of substrate and will take a few weeks to remove all of it. After a year or two, it all becomes very soft and easy to break into mud with the slightest pinch. Will need to be replaced yearly for the average person that likes to plant and rearrange things.

I suggest 1/2" to 1" of topsoil with osmocote fertilizer mixed in. Then cover with fiberglass screen material. Several rocks along the outer edges of the screen to hold it down. Then cap it with 2" to 4" of STS. The screen material prevents the topsoil from breaking out when a plant is uprooted. Allows plants to be disturbed more often without releasing too much nutrients into the water column and cause an algae outbreak. I also use a thin layer of heavier planting substrate to cap the STS. Makes it easier to plant stem plants or any buoyant pearling plants from floating up. After a few months the STS becomes heavier and easier to plant into.
Welcome to APC! Those are interesting suggestions. I always wash the dust out of substrate material like this. I would much rather do that than suffer the dust in the tank. And, the screen on top of the soil can result in a real mess if the roots of a plant get woven into the mesh, and you try to pull it up to replant it.
 

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Welcome to APC! Those are interesting suggestions. I always wash the dust out of substrate material like this. I would much rather do that than suffer the dust in the tank. And, the screen on top of the soil can result in a real mess if the roots of a plant get woven into the mesh, and you try to pull it up to replant it.
The roots will get stuck in the screen and will need to be cut with a knife. Most of my plants are carpeting plants with shallow roots. I have a few swords in the corners and just use my thumbnail to break the roots from the screen.

STS is so light that it doesn't trap any significant amount of gasses from the anaerobic areas. I find that I don't have any toxic hydrogen sulfide build up. Even with the organic top soil that has lots of wood pieces and plant material that will decompose. The substrate size is also big enough to allow plenty of flow to the lower layers. It's not like sand. The plant roots also help transport oxygen deep into the substrate. I keep the front short and slope it high towards the back. I've seen people use lava rocks or bricks to build height in the back and never heard of any issues with hydrogen sulphide gas problems. I feel like that's a myth and a scapegoat for other problems that occur.
 
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