# Saf-T-Sorb vs. Pool Filter Sand



## hoppycalif (Apr 7, 2005)

I have been using Saf-T-Sorb for a couple of years now, due to its very low cost and the belief that it should be a good substrate, but I think I have noticed that it doesn't do very well during the first few months in a planted tank. As I remember my experiences with pool filter sand were much better during those first months. 

About a year ago I modified a 10 gallon tank by putting an acrylic divider in the middle, making it a two 5 gallon tank, where both halves of the tank get exactly the same light at all times. That tank has rested in a closet for much of that year, when my attempt to put El Natural style set-ups in it didn't work at all well.

So, one of my friends here remembered that tank and hinted that I could do a comparison test between pool filter sand and STS. I just laughed at the idea, but it soon stimulated me to want to play scientist again.

So, I now have slightly modified the tank to make sure no water gets traded between the two halves, then purchased some pool filter sand and a new bag of STS (only to discover that I already had plenty of it stashed in an outdoor closet.) Tomorrow I will set it up with identical conditions, identical depths of substrate, identical plants (just a few), Identical water, identical fertilizing, and watch them for variations in how they make it through the first few months.

This will not be El Natural set-ups, but more like low medium light, with light fertilizing and API CO2 Booster dosed as recommended on bottle. My tap water is pretty soft, so I will dose both with GH booster to get close to about 6 dGH, to be sure there is calcium and magnesium for the plants. I don't plan to put any fish in the two tanks, but that is still undecided. The plants are easy to grow, beginner plants, possibly only 2-3 stems in each tank.

If I was an entrepreneur I would set up a betting booth and make some $$ on this! (But, I'm much too lazy to ever try that!)


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## mistergreen (Mar 3, 2007)

Nice! 
Try stems & rosettes. I wonder if the plant type matters.


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## Michael (Jul 20, 2010)

Great idea!

The recent discussion on STS led me to a hypothesis: STS gives better results with hard, high pH water (like mine) than with soft, low pH water (like yours and Diana's?).

Your experiment won't test this directly, but will give us some clues. If I were dedicated enough, I would set up the same tank as yours, only with STS on both sides and my hard tap water in one and some soft water in the other.


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## hoppycalif (Apr 7, 2005)

Today I got the tank filled with water and the two substrates, installed tiny filters in each half, and gave it a lot of thought - exhausting! The substrates I washed equally, 3 sessions with a hose, with the water being near clear when I quit. I taped a background to the back of the tank to make sure the near-by window doesn't affect the light intensity in the tanks.

I'm going to use plant cuttings - stem plants - from my existing tank, probably no more than 3 plants per tank. If I were to try to use rooted plants I would want to put a soil base under each substrate, and I don't have any rooted plants anyway, except 3 vals.

EDIT: My light intensity in both tanks is 34 PAR at the substrate. That is more than low light. The tanks are now planted, with 2 each rotala cuttings, probably rotala rotundifolia, and one hydrocotyle cutting. The cuttings are from the same plants and are very close to being the same size, and are planted in the same positions in each tank. I'm fertilizing every other day at the minimum level in the Estimative Index method, plus 0.5 ml of CO2 Booster daily.


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## hoppycalif (Apr 7, 2005)

My cell phone problems made it impossible to use the camera on it, so I bought a cheap camera on Amazon, and took my firs pic of the pair of tanks: You can see the most obvious difference between the two substrates. The pool filter sand is many times more reflective than the STS. It doesn't have an significant effect on PAR, but it does make looking at the two side by side very difficult. Next pics will be one half at a time.


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## GadgetGirl (Sep 25, 2013)

Subscribed to this thread! Very interested in your results as I'm a huge STS/Oil-Dri fan and dislike sand because it always ends up looking so bad. Purely esthetic reasons.


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## hoppycalif (Apr 7, 2005)

I tried photographing the tank(s) with the light off, and using the flash. It looks a little easier to see.


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## GadgetGirl (Sep 25, 2013)

Are you going to measure ph & KH?


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## mistergreen (Mar 3, 2007)

STS looks pretty good.


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## hoppycalif (Apr 7, 2005)

GadgetGirl said:


> Are you going to measure ph & KH?


Yes, I plan to measure GH, KH, NO3, and perhaps pH every week.


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## hoppycalif (Apr 7, 2005)

mistergreen said:


> STS looks pretty good.


I really like the looks of the STS as a substrate, but absolutely dislike that of that particular pool filter sand. In general I like dark colored substrates best, and the mix of brown and black with STS looks very good to me.


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## hoppycalif (Apr 7, 2005)

mistergreen said:


> STS looks pretty good.


I really enjoy the look of the STS substrate, and hate the look of this particular filter sand. In general I like dark substrates best, with a mix of black and brown best of all.


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## hoppycalif (Apr 7, 2005)

About 5 days since the water has been in the two tanks:

-----Pool Filter Sand ------------ Safe T Sorb 
pH -----------7.6 ----------------- 6.0 
GH ---------4 dGH ----------------6 dGH 
KH --------- 2.5 dKH ------------ 0.5 dKH 
NO3 --------10 ppm --------------10 ppm ---(From fertilizing) 

I wasn't expecting this, and I'm not sure why the differences.


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## mistergreen (Mar 3, 2007)

Interesting that GH went up. I'd expect it to go down like pH & KH.


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## hoppycalif (Apr 7, 2005)

mistergreen said:


> Interesting that GH went up. I'd expect it to go down like pH & KH.


If the STS is removing cations from the water you would expect the calcium, magnesium and potassium would be removed, lowering the GH. In a couple of days or so I will repeat this and see if it is just mistakes I made. I also want to do the same testing on my 30 gallon tank, which also has STS substrate, but also has a GH booster added to raise the GH.

The 3 plant cuttings are all still alive in both sides.


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## GadgetGirl (Sep 25, 2013)

What GH & KH test kit do you use?


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## hoppycalif (Apr 7, 2005)

I have a Nutrafin GH/KH test kit, which is about 3 years old. It seems to still work ok.

I just tested the water in my 30 gallon tank, which has a STS substrate. I have 6.0 or lower pH, 1 or lower dKH, and about 4 dGH, very similar to that in the 5 gallon tank. It was set up about a month or so ago, and the plants are growing, but not with the vigor I expected. Obviously we can't assume that STS is comparable to sand, as far as its effect on the water is concerned.

Maybe a high CEC can be too high?


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## GadgetGirl (Sep 25, 2013)

I don't know anything about that particular brand but I know the API kit expires pretty quickly.

Edit: I just looked at my kit. It does last 3 years. Just got it this year and GH expires in 2023.


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## GadgetGirl (Sep 25, 2013)

That sounds very similar to my Oil Dri cap. KH dropped from 3.0 in tap water to 0 after setup. And ph dropped from 7.0 to < 6. I've been adding baking soda to compensate.


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## mistergreen (Mar 3, 2007)

Interesting. An alternative to making soft water for breeding fish.


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## GadgetGirl (Sep 25, 2013)

Would probably work for awhile, but it eventually equilibrates when all the sites are bound. I'm keeping track of it this time.


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## hoppycalif (Apr 7, 2005)

I rarely test my water having found that I didn't gain anything from doing it, but apparently we have to do so with Safe T Sorb as a substrate or cap. It looks like I can add a half teaspoon of baking soda to 30 gallons and gain about 1 degree of KH. Then I can monitor the KH and stop adding the bicarbonate once the KH stops dropping.

For my two 5 gallon tank test, I'm still thinking about whether I should tinker with the water or just let it go to see what the effects are.


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## GadgetGirl (Sep 25, 2013)

I think you should just let it go to see what happens. Great experiment!


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## hoppycalif (Apr 7, 2005)

My reason for doing this test is that it looks like when I use STS as a substrate my plants are reluctant to start growing. I still don't know if that is really what I experienced or just seems that way. So, the experiment continues!!


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## hoppycalif (Apr 7, 2005)

Here is how the two tanks look this morning. Still no obvious difference between the plants in them.


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## GadgetGirl (Sep 25, 2013)

What are your pH, GH & KH doing?

Do you think you need more plants in there?

Thank you for taking the time to do this experiment!


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## hoppycalif (Apr 7, 2005)

About 12 days since the water has been in the two tanks:

-----Pool Filter Sand ------------ Safe T Sorb 
pH -----------7.6 -------------------6.0 
GH ---------4 dGH ----------------6 dGH 
KH ----------2.5 dKH --------------0.5 dKH 
NO3 --------40 ppm ---------------40 ppm

My daily weak dosing of ferts is why the NO3 is increasing.



GadgetGirl said:


> Do you think you need more plants in there?


I would like to have a couple more plants in each, but I didn't have any when I started, and I don't want to prune my plants to get more now. It shouldn't make any difference though.

I can understand why the very high CEC of STS would remove cations from the water, but carbonates/bicarbonates are not cations, so why should the KH drop so much?


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## mistergreen (Mar 3, 2007)

Does calcium carbonate show up on KH?


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## hoppycalif (Apr 7, 2005)

mistergreen said:


> Does calcium carbonate show up on KH?


KH is a parameter of the water, so anything that dissolves in water, as calcium carbonate does, will show up as part of the KH and GH. As I understand it, CEC results in the positive calcium ions attaching to points on a solid, where plants can pluck them for food. So, the carbonate ions from calcium carbonate should remain in the water???


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## mistergreen (Mar 3, 2007)

hoppycalif said:


> So, the carbonate ions from calcium carbonate should remain in the water???


Don't know about that. Cation doesn't split molecules. That would require energy. I'm thinking it would grab CaCO3, not Ca, and split CO3 floating around.

I think it's the plant roots that actively get what they need like Ca ions, etc.. They would send out H+ ions from what I remember reading.


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## hoppycalif (Apr 7, 2005)

mistergreen said:


> Don't know about that. Cation doesn't split molecules. That would require energy. I'm thinking it would grab CaCO3, not Ca, and split CO3 floating around.
> 
> I think it's the plant roots that actively get what they need like Ca ions, etc.. They would send out H+ ions from what I remember reading.


If I was a lot younger I would take some college courses to learn about this stuff. If I try that now I would learn it today and forget it tomorrow


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## mistergreen (Mar 3, 2007)

> Calcium is naturally present in water. It may dissolve from rocks such as limestone, marble, calcite, dolomite, gypsum, fluorite and apatite. Calcium is a determinant of water hardness, because it can be found in water as Ca2+ ions. Magnesium is the other hardness determinant.
> 
> Read more: https://www.lenntech.com/periodic/water/calcium/calcium-and-water.htm#ixzz6d360Y0Xg


Ca ions float around in water too.



> Calcium carbonate will react with water that is saturated with carbon dioxide to form the soluble calcium bicarbonate.
> 
> CaCO3(s) + CO2(g) + H2O(l) → Ca(HCO3)2(aq)


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## hoppycalif (Apr 7, 2005)

mistergreen said:


> Ca ions float around in water too.


Water can't have a surplus of positive or negative ions. If there are calcium ions in the water, there must also be an equal number of negative ions, like sulphate, chloride, etc. If a mineral has a cation exchange capacity I assume that means a positive ion in the water replaces a positive ion that was part of the mineral. How does that cause the STS substrate water to become low in KH?

"Calcium carbonate will react with water that is saturated with carbon dioxide to form the soluble calcium bicarbonate. CaCO3(s) + CO2(g) + H2O(l) → Ca(HCO3)2(aq)" Water doesn't get saturated with CO2, or, at least is doesn't need to have that much dissolved CO2 before calcium carbonate reacts with the CO2. As more and more CO2 dissolves in the water the water becomes more lower in pH as the Carbonic Acid percentage increases. I recall vaguely that the lowest pH that Carbonic acid can cause is around 5.5. I don't know why that is the case unless it is due to saturation with CO2?


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## mistergreen (Mar 3, 2007)

hoppycalif said:


> If there are calcium ions in the water, there must also be an equal number of negative ions, like sulphate, chloride, etc.


I'm sure there a a bunch of different ions floating around like how iron ion is made by UV (energy).



hoppycalif said:


> If a mineral has a cation exchange capacity I assume that means a positive ion in the water replaces a positive ion that was part of the mineral. How does that cause the STS substrate water to become low in KH?


I wish I have a phd in water chemistry. But isn't it just a matter of charge attraction? The negative charge of the substrate (STS), attracts positive nutrient ions.


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## hoppycalif (Apr 7, 2005)

mistergreen said:


> I'm sure there a a bunch of different ions floating around like how iron ion is made by UV (energy).
> 
> I wish I have a phd in water chemistry. But isn't it just a matter of charge attraction? The negative charge of the substrate (STS), attracts positive nutrient ions.


I don't know a lot of things, like why women do what they do, why a dog can connect with a human so totally, and if it is just a matter of charge attraction.[smilie=b: Maybe we should use our "social distancing" time to get a PH degree in Aquariums, (PhA?) and there will be one less thing we don't know.


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## mistergreen (Mar 3, 2007)

I did a little reading, see if this conclusion is right. KH doesn’t measure CaCO3 directly. It measures CO3 & HCO3. CaCO3 is sort of insoluble But is soluble in low pH, acids like tannic, carbonic, etc..The byproduct of CaCO3 and the acids create CO3 & HCO3. I have no idea why the KH would drop, maybe they combine with other ions and precipitate out?

Also, maybe the GH rises is due to the lower pH. The lower the pH, More H+, the more ions is release from the STS. That seems to be the rule of CEC and why plant roots release H+ to get ions in the substrate.


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## hoppycalif (Apr 7, 2005)

It is looking more and more like the STS may be winning this contest! The Rotala plants are growing better in the STS, and the hydrocotyle is growing a little faster in the pool filter sand. But the appearance of the STS is much better than the sand.


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## mistergreen (Mar 3, 2007)

Funny, my stems aren't doing so great in sand also. I put in osmocote in the sand to see if it helps.


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## GadgetGirl (Sep 25, 2013)

Yay! +1 for STS! I'm rooting for it.  Haha! Get it... rooting? I'll see myself out....


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## hoppycalif (Apr 7, 2005)

GadgetGirl, I'm speechless!


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## hoppycalif (Apr 7, 2005)

Measured water parameters again, today:

---------Pool Filter Sand -------- Safe T Sorb 
GH -----------3 dGH----------------7 dGH 
pH -----------7.6 -------------------<6.0 
KH ----------2 dKH ----------------0.5 dKH 
NO3 --------Not Checked----------80 ppm 

My daily weak dosing of ferts is why the NO3 is increasing.


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## mistergreen (Mar 3, 2007)

I think you can stop dosing ferts.


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## hoppycalif (Apr 7, 2005)

mistergreen said:


> I think you can stop dosing ferts.


You are probably right. Three little plants don't use up much of the nutrients. I might just stretch the time between dosing, just in case only the nitrates are over dosed. Actually, I'm about ready to conclude that my fear that STS was inhibiting plant growth is not valid.

Another place where STS is better than pool filter sand is the brown scum now starting to cover the sand, while the STS still looks totally clean. The glass is also getting more brown scum, by far, than the STS tank. And, of course, the STS looks great compared to the sand.

The best result of this "adventure" is finding out how well this works for evaluating the effect of "stuff" on the aquarium.

I still don't understand the chemistry that is causing the low KH and higher GH in the STS tank.


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## mistergreen (Mar 3, 2007)

I think the excess nutrients is helping the brown diatom.


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## hoppycalif (Apr 7, 2005)

mistergreen said:


> I think the excess nutrients is helping the brown diatom.


But, only in the sand substrate tank, not the STS substrate. Why???


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## Michael (Jul 20, 2010)

Perhaps the sand substrate is contributing an algae nutrient (silicates) that STS does not?


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## mistergreen (Mar 3, 2007)

My only guess is sand reflects light. Algae needs light.

I have an unlit tank next to a lighted tank. The brown diatom grows on the side in the unlit tank where the light is coming from.


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## mistergreen (Mar 3, 2007)

Michael said:


> Perhaps the sand substrate is contributing an algae nutrient (silicates) that STS does not?


Yeah, I was thinking about the silicate too but the STS clay is a silicate but it has other elements like Al, Na, Ca.


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## hoppycalif (Apr 7, 2005)

Here are a couple of pics of the two tanks - put side by side as they are. I did it this way to avoid the different brightness problem. Notice that the rotalas are growing much better in the STS, while the other plant is doing slightly better in the sand - in the sand it is growing towards the front, while in the STS it is growing to the right side. Why???


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## mistergreen (Mar 3, 2007)

I have a rotala stem that grows sideways for no reason while the other stems are normal. Notice the roots growing out of each node.

** Not sure if it's because too much light or not enough **


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## hoppycalif (Apr 7, 2005)

I ended this test today, and was shocked by what I found: the Rotalas in the STS substrate had much bigger roots than those in the pool filter sand. The difference is about a factor of 4. No wonder the STS Rotalas grew so much better. The Hydrocotyl plants didn't have nearly that big a difference in roots, but the one in the STS was a bit bigger root mass.

This can be caused by at least 2 diffferent things: One, the STS has larger particles, so there may be more room for roots. Second, the STS high CEC may encourage root growth. A way to determine which of the two is more likely is to use a sieve to remove the fine particles in the sand, leaving roughly the same particle size as the STS. If the plants then grow about the same as in the STS it might just be the particle size making the difference. But, I'm not going to do that, for now. I have another test to do first.

Next, I am going to see if API CO2 Booster results in better plant growth. https://www.aquaticplantcentral.com...5301-testing-api-co2-booster.html#post1012593


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## davemonkey (Mar 29, 2008)

Thanks for posting the results, and for doing the trial in the first place. This experiment was informative and useful for the hobby!


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## mistergreen (Mar 3, 2007)

STS - 1 
sand - 0


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## Seattle_Aquarist (Mar 7, 2008)

hoppycalif said:


> I ended this test today, and was shocked by what I found: the Rotalas in the STS substrate had much bigger roots than those in the pool filter sand. The difference is about a factor of 4. No wonder the STS Rotalas grew so much better. The Hydrocotyl plants didn't have nearly that big a difference in roots, but the one in the STS was a bit bigger root mass.
> 
> This can be caused by at least 2 diffferent things: One, the STS has larger particles, so there may be more room for roots. Second, the STS high CEC may encourage root growth. A way to determine which of the two is more likely is to use a sieve to remove the fine particles in the sand, leaving roughly the same particle size as the STS. If the plants then grow about the same as in the STS it might just be the particle size making the difference. But, I'm not going to do that, for now. I have another test to do first.
> 
> Next, I am going to see if API CO2 Booster results in better plant growth. https://www.aquaticplantcentral.com...5301-testing-api-co2-booster.html#post1012593


Hi @hoppycalif

Good experiment and the results don't surprise me. Along with the higher CEC in STS (verses zero CEC in sand) and other calcined clay substrates they also contain large amounts of micro-nutrients (and potassium) which are relatively easy for plant roots to access and utilize. Here is a table that was part of an article in Planted Aquaria Magazine (PAM) Summer 2000 issue. Look at the CEC and nutrient levels of the various calcined clay materials (#8, #16, #16a, #17) verses Flourite (#19) or sand (#21). -Roy

Reprinted from Planted Aquaria Magazine (PAM) Issue #2 Summer 2000


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## hoppycalif (Apr 7, 2005)

Roy, that is a great table to keep in our brains! I don't recall ever seeing it before.

Maybe plants grow lots of roots when there are lots of nutrients available to the roots, but only a few anchorage roots when there aren't lots of nutrients?


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## davemonkey (Mar 29, 2008)

hoppycalif said:


> Roy, that is a great table to keep in our brains! I don't recall ever seeing it before.
> 
> Maybe plants grow lots of roots when there are lots of nutrients available to the roots, but only a few anchorage roots when there aren't lots of nutrients?


I would think compaction would have an impact as well (sand is more "compact" than STS, for example). In a farming situation, crops will develop deeper and more robust roots in soil that has been minimally tilled (which means less heavy equipment traffic and less disturbance of soil structures) than in conventional settings, even in the same soil series (same nutrient load). Soil Heath scientists have found that the less disturbed a soil is, the more air space/pore space exists, which translates into larger root mass.


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## hoppycalif (Apr 7, 2005)

davemonkey said:


> I would think compaction would have an impact as well (sand is more "compact" than STS, for example). In a farming situation, crops will develop deeper and more robust roots in soil that has been minimally tilled (which means less heavy equipment traffic and less disturbance of soil structures) than in conventional settings, even in the same soil series (same nutrient load). Soil Heath scientists have found that the less disturbed a soil is, the more air space/pore space exists, which translates into larger root mass.


That would be my first guess on why the root masses were so different. Maybe my next experiment will be sand with the "fines" removed vs. regular sand. I have almost a full bag of sand left over so it would be fairly easy to do. And, that might make the sand more like gravel - less compacted.


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## mistergreen (Mar 3, 2007)

Would STS make a good filter media or do they break down overtime?


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## hoppycalif (Apr 7, 2005)

Filters are not supposed to change the parameters of the liquid being filtered. They are supposed to remove particles. If you run water through STS, as a filter media, it will probably drop the pH and KH of the water as it goes through. In addition, it would shed very fine particles which would end up in the "filtered" liquid. I doubt that using it as a filter media would be anything worth doing.


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## DartPraidon (Mar 12, 2021)

I have filters stop working, and any and despite the companies and models. They just stop filtering over time, and it doesn't take 2-3 months. What do you think it's about?


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## hoppycalif (Apr 7, 2005)

I suggest you submit this as a new thread, so people who could answer it will see it.


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## DartPraidon (Mar 12, 2021)

DartPraidon said:


> I have filters stop working, and any and despite the companies and models. They just stop filtering over time, and it doesn't take 2-3 months. What do you think it's about?


Btw, I was really very desperate and thought and went to look for something on my favorite site that is about pools like skimmer basket and maybe I will find something in common between the aquarium and the pools. I decided to take a very powerful pump that will maintain the temperature of the aquarium, It remains only to populate my favorite fish, I have 13 species, the main thing is that the algae do not die under such conditions. Please wish me good luck, so that everything goes well and without problems.


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