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High CEC sand?

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I'm thinking of swapping out Eco complete for a sand to be better for my corydoras. Are there any fine sands that have a high or moderate CEC? If not, are there any high CEC materials that could go under the sand but wouldn't need replacing like soil would? Would relatively hard clay balls work well under sand?
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No sand has high CEC. By its very definition it cannot.

Cationic Exchange Capacity is only possible on extremely small particles. Small enough to carry a charge. Clay particles and Humus particles are in this size range.

Clay can bind together to become larger bits without losing the ionic properties.
Materials like Montmorillonite clay make good aquarium substrates for this reason.
Oil Dri
certain brands of Kitty Litter (do a search here, and read which ones hold up and which turn to mush)
Safe-T-Sorb (available at Tractor Supply and other places)
Turface (a sports field material available at irrigation and related stores like John Deere, Ewing and others)

ADA product line also has pretty high CEC.

Some peat moss is fairly good at it.

Why not just build a sand area into the tank without swapping out all the substrate? Look at some of the 'scapes with a sand path, or area at the front.
 

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Discussion Starter · #3 ·
Thanks Diana. I've started looking into some of those. I thought of turning part of the tank into a cory sandbox, but with the way they like roaming all over the tank I wasn't sure whether they would focus on the sand enough to make a difference. Any experience with that?
 

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I'm thinking of swapping out Eco complete for a sand to be better for my corydoras. Are there any fine sands that have a high or moderate CEC? If not, are there any high CEC materials that could go under the sand but wouldn't need replacing like soil would? Would relatively hard clay balls work well under sand?
Forgive my ignorance, but why is the change better for your cory's? Could you put a sand cap on the Eco-complete? As was previously mentioned, sand has little (if any) CEC.
 

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Discussion Starter · #5 ·
Forgive my ignorance, but why is the change better for your cory's? Could you put a sand cap on the Eco-complete? As was previously mentioned, sand has little (if any) CEC.
I haven't tried it, but my understanding was that the sand would eventually settle and the larger eco complete pieces would work up to the surface and it wouldn't make much of a difference in the long run.
 

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It may depend on the density of the Eco-Complete vs. Sand. I was under the impression that the finer particles will remain on the top and coarser on the bottom. I'm in the process of planning my Discus tank, which will have some plants. I planned on trying to keep the sparse planted areas separate from open water (120 Gal amazon basin). I was going to layer the planted areas with Volcanit-Euro M & F in the planted areas. The unplanted areas would be a mix of Carib-Sea's Peace River and Crystal River substrates. The Vulcanit will be topped with the Crystal River which is the consistency of sugar. I'm hoping it works.

Bump: PS: I'm planning Bristlenose Pleco's and Farlowella for my scavengers.
 

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Discussion Starter · #7 ·
Interesting. My understanding was that it was the opposite; the fine grains would sink down between the larger gravel and push the gravel up. That seems to happen within the varied grain sizes of eco complete on its own.
 

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Discussion Starter · #9 ·
I wasn't saying there was any gravitational difference based on size, just that sand will fit down the gaps between gravel pebbles, but gravel can't fit down the smaller gaps between sand grains.
 

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Gravity does not care about size. Density mattters. With time, denser material will end up at the bottom. No matter the particule size. At the same density, smalle material will simply fill the "voids" that exist within the larger material.
Very true, but also take a look at nature. If you look at the delta and other water ecosystems, the finer particles do end up on top. They also compress to some degree. If you start with the coarser material and grade it upwards the finer material will stay on top. (Also consider how they build roads, big stuff on the bottom and grade upward).
 

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Very true, but also take a look at nature. If you look at the delta and other water ecosystems, the finer particles do end up on top. They also compress to some degree. If you start with the coarser material and grade it upwards the finer material will stay on top. (Also consider how they build roads, big stuff on the bottom and grade upward).
I agree. Anything man made tend to defy the gravity. That is why I said "with time..." Give the road a couple of hundred years and a few earth quakes or floods :).
 

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Interesting. My understanding was that it was the opposite; the fine grains would sink down between the larger gravel and push the gravel up. That seems to happen within the varied grain sizes of eco complete on its own.
You are correct. Fine will sink. This is why most avoid capping with fine sands. Eventually the two substrates will start blending and there is a good chance, you won't like the results.

We are talking about aquariums here, not nature. Natural depths of water generate much higher pressures than any of our tank can. The deeper you go, the more pressure exerted on the bottom. I have never been deep sea diving or to the bottom of a river for say but I am sure any sand covered bottom is a cap that is much deeper than our aquariums. Therefore, one can not say the fine sand stays on top. At 1-3ft+ deep, its all on top.
 

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Agreed, the finer particles will eventually work their way to the bottom, as long as the fine particles are dense enough to sink at all. This is basic physics when you consider the geometry of the problem.

It doesn't matter if the large particles are more dense or not. They'll hit the bottom first because of this. However, large particles end up with large gaps between them. Fine particles fit through these gaps, with at least some of them ending up under the top layer of large particles.

Now, if you gently disturb the substrate (ie: shake it without completely removing everything, like what happens as we do tank maintenance like planting plants), the fine particles that are under the top layer will find opportunities to work their way under the next layer, and more fine from the top will work under the first.

If you keep disturbing the substrate, over time the fine particles work deeper and deeper between the coarse particles. Eventually the fine particles will reach the bottom. Once they are there, they will form a tightly spaced layer. The gaps in this layer are too fine for large particles to slide between, so this effectively prevents the large particles from ever getting down under the fine.

Don't believe it? Put some gravel in a cup, top it with sand, gently shake and watch what happens. You'll quickly see the gravel resurface.



I'm thinking of swapping out Eco complete for a sand to be better for my corydoras.
I, personally, think the idea that corydoras need sand substrates and that substrates like eco-complete erodes their barbels is a pile of horse manure. Corydoras are most commonly found in nature in silty areas of slow moving streams, but that's because there's plenty of food there. However, they are also found in gravelly areas in nature, and it doesn't seem to be killing them off.
 

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Flourite Dark or fluorite Black have fairly high CEC and one or the other is what my sister uses and it looks like fine sand.
Only fluorite I have used was red fluorite and it was many year's ago.

Quick google fluorite black sand.
 

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Discussion Starter · #15 ·
Thanks for the additional discussion and info.

I know there is debate about the effects of gravel substrate on cory barbels. I've been coming around more to the idea that barbel erosion is related more to water quality and/or infection, but I figure if it could possibly help it's probably worth giving it a shot.

This may not work, but I've been thinking about the idea of putting some larger clay balls or lava rock in a medium nylon mesh bag anchored to the bottom of the tank with silicone so that sand could sink down in and roots could reach in, but the larger chunks couldn't rise to the surface as long as there is enough sand to cover the bags. I imagine the biggest risk would still be anaerobic pockets forming as sand compacts between the larger media pieces. Does this seem like a workable idea? I may try it out in a jar or bucket just to test it on a small scale that can be easily agitated to accelerate settling.
 
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