# High CEC Substrate worse than low CEC inert? Cation Exchange Capacity



## WaterLife (Jul 1, 2015)

Are high CEC substrates, such as Safe-T-Sorb, Turface, Eco-Complete, Flourite, etc., worse that just using a plain low CEC inert substrate?

Deciding between using Black Diamond Blasting Sand (inert, low CEC), or Safe-T-Sorb ("inert", but high CEC).

Most might say the high CEC sub is better since it will absorb nutrients for the plant root.

However I've heard of high CEC substrates striping away the carbonates from the water, thus it should lower KH, taking away the water chemistry's stability/buffer, which can cause pH fluctuations or make the water acidic. Sounds like a pretty big concern to me. My KH is only 3 dKH out of the tap. Anyone know how much carbonates the substrate would strip away (how much would it lower KH?)?

Second thing that comes to mind, is if it retains too much nutrients, possibly causing toxicity for plants, and/or makes dosing (EI or PPS) more tricky (since you don't know how much nutrients are already in the tank/in the sub). I would assume it would depend how much/how thick the layer of high CEC sub you have.
Or if the high CEC sub pulls too many nutrients out of the water column, taking away from the plants that primarily do intake from their leaves and not their roots.

From experiments I've seen with inert low-CEC sub, is that most plants do really well just water column feeding, although heavy root feeders could do with a little extra nutrients (root tabs) in the sub.
But I don't foresee the issue mentioned above using this type of sub, so it doesn't have the high CEC benefits, but it also doesn't pose the same (worse imo) issues.

Thoughts? Experience/results/growth comparison?
(for my purpose the tanks would be high light, heavily planted, co2, full ferts)



Just some other side questions. I have read that Safe-T-Sorb, BDBS (coal slag) and even Silica sand can cause health issues, even cancer, is that really a concern for aquarist or the fish in the tank? Or are those health issues just a realistic concern for those that work with the material daily in factories/shops, with the main risk from exposure to the material in dust form (breathe it in)?

For BDBS, I actually like the fine grain sand (so do burrowers and sand sifter fish) vs the medium, but is the fine sand too light that it clouds the water/remains suspended long, or just too light to hold down plants easily?

Which Safe-T-Sorb is the correct one to get for planted aquarium use?

Just comparing these substrates, not enriched substrates or soil.


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## roadmaster (Nov 5, 2009)

As my low energy tanks are long term set up's (year or more), I like substrates with good CEC.( I make them with soil,peat,catlitter.)
I count on the nutrient's in the substrate to provide for the plant's in addition to water column dosing.(1/3 EI values). Is win/win for the plant's I think.
The black diamond 20/40 grit is what I use,The 30/60 grit is indeed very fine, and can cause issues with some stem plant's staying rooted.
Fishes and shrimp's do well over the black diamond over the three plus year's I have used it.
Cannot speak to the safety sorb for I have not used it (yet).
Other's have with good success.
I do not believe the high CEC substrates would strip away anything at a rate that weekly 50 % water changes would not replenish before it became an issue, but I keep seachem equilibrium on hand in case it might be needed.


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## thedood (May 30, 2015)

You can always pre-charge safe-t-sorb, some may say mineralize it, to prevent the further absorption of carbonates once it is placed in your water column. There is a thread where one of the members tested different charge recipes using ferts. Pretty interesting reading. I myself have avoided using sts out of fear of creating unstable water chemistry at the beginning. I am working on setting up a 20H native tank and am thinking of going precharged sts. For precharge I was thinking of going with just high kh water changed weekly and monitoring the hardness and ph changes and doing so for a month which would be four changes. I would gladly team up with you on a thread dedicated to testing absorption rates of carbonates by sts since we may very well have very different water. My water out of the tap is low mid 8 ph and kh 13 gh 9/10 or so. 

I have been using the 30/60 bdbs, I have it in two planted tanks and one cichlid rock scape tank, I have been pleased with the results and the rock stable water chemistry. The planted tanks are yard dirt capped with bdbs and I use home made O+ root tabs near the root feeders. 

As far as cancer and health risks the problem is inhaling the dust. Silica sand used in sandblasting environments is done with a suit and air supply. I doubt there is much risk to fish as the dont inhale the dust. I dont think I would want my fish swimming around in a new tank that had these subs used unwashed until the fine particles were filtered out and or settled as I imagine those particles may irritate gills but that is a guess on my part.


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## Nordic (Nov 11, 2003)

My corydoras paleatus always seem to do a good job of getting the finest sand and dust buried quickly... and finding any rocks or gravel hidden in the sand. It may as well be made of cork.


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## Seattle_Aquarist (Jun 15, 2008)

WaterLife said:


> Are high CEC substrates, such as Safe-T-Sorb, Turface, Eco-Complete, Flourite, etc., worse that just using a plain low CEC inert substrate?
> 
> Deciding between using Black Diamond Blasting Sand (inert, low CEC), or Safe-T-Sorb ("inert", but high CEC).
> 
> ...


If you would like to read a really good article on CEC along with a table of substrates with mineral contents and CEC values check out page 17 of Planted Aquaria Magazine found here.

Hi WaterLife,

I don't know if I would characterize high CEC (cation exchange capacity) substrates as better or worse than any other substrate - it depends upon what you are trying to achieve. Some substrates have little no CEC (like sand and gravel), some substrates are low CEC (like Flourite; note Flourite is a low CEC product), and some have a high CEC such as the calcined montmorillonite clay products (Turface, Safe-t-sorb #7941, others).

I originally started with plain natural gravel in my planted tanks eight years ago. They were absolutely fine and I grew some nice plants in them with DIY CO2 and Seachem fertilizers.

Natural Gravel, DIY CO2, Seachem ferts









About six years ago I set up my first tank with a calcined montmorillonite clay product (Turface Pro League Grey - discontinued) and was amazed at the results. The plants definitely grew faster for me.

Marsilea minuta after planting 12/10/09









Marsilea minuta on 1/4/10 (3.5 weeks later)









Same 30 gallon approx 1 month after planting









Yes, high CEC products absorb nutrients (in my case from the water column since I do estimative index/EI dosing with dry ferts) and make those nutrients available to the plants in the root zone. Unlike inert or low CEC substrates high CEC substates continue to provide nutrients to the plants even if I neglect EI dosing for several weeks. 

Yes, high CEC substrates will absorb the carbonates from the water initially (sometimes a month or longer) resulting in a lowering of the dKH and to a lesser extent dGH. I have not had any issues with fish or plants as a result of low dKH. What I have done with a tank that has new high CEC substrate is check my dKH weekly and adjust it up to where I want it to be. Eventually the substrate stops absorbing the carbonates and reaches an equilibrium and the only carbonates that are used are by the plants. My dKH here in Seattle is typically 2.0 or less so I try to adjust it up to about 4.0 dKH. When I first fill a tank with new substrate my dKH can drop to less than 1.0 dKH. Here is a good article explaining CEC in soils.

In the six years I have been using high CEC substrates I have not had any issues with toxicity. Since it is the plant that determines the amount of nutrients it will receive (by growing more roots) the plants only receive the nutrients they need. That said, I do find that Cryptocorynes and chain swords (Helanthium previously Echinodorus) do benefit from the addition of root tabs near their bases.

As I stated I do all of my fertilizing through the water column via the EI method with the addition of root tabs near the base of some species. It is my belief that most aquatic plant species absorb nutrients both through their leaves as well as their roots - some plants just seem more efficient at one method or the other. By dosing the water column and using a high CEC substrate I give my plants to absorb nutrients through their leaves, roots, or both.

As for safety concerns most clay products (like cat litter) contain a small percentage of crystalline silica, I would not suggest breathing the dust for long durations of time; it will not effect the fish.

Safe-T-Sorb #7941 (green 40# bag) - $6.49 at Tractor Supply Co.


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## Maryland Guppy (Dec 6, 2014)

http://www.plantedtank.net/forums/29-substrate/883065-safe-t-sorb-substrate.html

Here is the thread I sort of hi-jacked.
My revised pre-charge recipe is at the end.










I've been tossing plugs of plants it there as I trim other tanks.
If I leave the plug for a few days in one spot the roots take off like crazy.
Split some anubias last night and just added.
I'm slowly testing plant variety in here.
One bunch of Ambulia melted within 48 hours, who knows.
This tank has no CO2 and less light, probably caused the melt???


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## dukydaf (Dec 27, 2004)

In my experience with soil, peat and ADA Aquasoil, in % of soil /water found in normal aquariums it will not be enough to reduce the KH to 0. This of course depends on your starting KH. To give you an idea starting with KH 13 , I got KH 7 . Same substrate, starting with KH 3, KH remained 3. 

Second, high CEC substrate will not draw certain nutrients from the water ( -NO3 for eg. ) and in a similar fashion to KH it will not bring others to 0 (under normal %). The binding of nutrients is not very strong and varies with pH. Toxicity of nutrients under EI or PMDD is very doubtfull in most conditions. Furthermore, some nutrients in any substrate are not in bioavailabe form. Bottom line, with a tank of your description - full ferts- a high CEC substrate will not be problematic. I find that plants root better in high CEC substrates and the substrate is capable of covering small hiccups in fertilizing. Plus shrimps love a buffering substrate  That being said, once sand or gravel has enough mulm, plant performance is similar (speaking of heavy root feeders here). 

Most of the health problems associated with sand come from aerosolized particles in high doses. This mostly happens when we setup the aquarium. Given that this is done once and very rarely, I will say it is not a risk for aquarists.


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## Diana (Jan 14, 2010)

STS and related materials (Turface, Soil Master Select- not available any more) can remove all the KH. 
Tap water KH usually 4-5 German degrees of hardness. 
KH in many of these tanks (I have several tanks with all 3 materials) drops to 0. The pH drops to the bottom of the hobby level testing equipment (Jungle Strips, Tetra Strips, API, and swimming pool tests) It too lab quality pH strips to see it was in the very low 5s. Many of my tanks have driftwood, peat moss in the filter, or both. 
Tanks with coral sand, oyster shell grit or that I more often dose potassium bicarbonate tend to stabilize, and maintain whatever KH and pH I want. 
For Lake Tanganyika I blended 50/50 coral sand and Turface. (Looks ugly, but no way to separate them now). This is enough coral sand to stabilize the KH in the range preferred by rift lake fish. 

Most of my tanks are low tech, with glute for carbon. When I skip dosing ferts for a while the plants are fine. There is enough reserve in the substrates to keep them rich green and growing.


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## dukydaf (Dec 27, 2004)

Thank you Diana for the info- I am not familiar with what STS stands for? Standard top soil  ? If you don't mind me asking how long did it take for the KH to drop from 5 to 0 ? Could it be that plants helped in lowering the KH ?

No matter where I moved in the EU I still encounter hard water, so lowering the KH from 13 to 7 was a welcomed change. To give a little more details about my aquarium, the aquarium had ADA AS. 6 months with daily tap water changes , KH drop from 13 to 7 in a week's time. Switched to RO and it took me about 4 months to lower the KH. By the end of the week the old ADA AS would raise the KH.

Once your KH is 0, adding peat will recreate bog conditons with the associated low pH. Do you have tanks with both oyster shell/ other carbonate sources and peat ? What would be the advantages of such a setup ?

Thanks


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## Hoppy (Dec 24, 2005)

CEC is "cation exchange capacity". Cations have positive charges. Carbonate is an anion, with negative charge. How does a high CEC substrate remove carbonate ions from the water? I vaguely recall someone, probably Diana, explaining this some time ago, but I don't recall the details.


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## mossback (Aug 12, 2010)

Hoppy said:


> CEC is "cation exchange capacity". Cations have positive charges. Carbonate is an anion, with negative charge. How does a high CEC substrate remove carbonate ions from the water? I vaguely recall someone, probably Diana, explaining this some time ago, but I don't recall the details.


When I became acquainted with turface, etc, I asked myself the same question. 

Apparently the soil science folks discovered that a clay surface contains negatively charged exchange sites, which attract cations. They defined CEC as a measure of the number of such sites relative to the mass of the clay. See 
Cation Exchange Capacity in Soils, Simplified for background -- it even refers to montmorillonite. 

The existence of high-CEC clays that also adsorb carbonate ions suggests that a clay surface containing negatively charged sites might also contain positively charged sites. These would (1) balance out the negatively charged sites, and (2) attract anions like carbonate. So personally I am OK with using CEC as an indirect measure of carbonate adsorption capacity.


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## Hoppy (Dec 24, 2005)

mossback said:


> The existence of high-CEC clays that also adsorb carbonate ions suggests that a clay surface containing negatively charged sites might also contain positively charged sites. These would (1) balance out the negatively charged sites, and (2) attract anions like carbonate. So personally I am OK with using CEC as an indirect measure of carbonate adsorption capacity.


If a substrate or any other substance adsorbs cations and anions, it would not be useful in our tanks, since it would mostly hold only calcium cations and carbonate anions. Both of which would be in higher concentration than virtually all of the other ions. So, I don't think that is a likely reason for the KH reduction.


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