# Pumice substrate



## Kalle (May 14, 2010)

I've been thinking a lot about what substrate to use and have been looking into what I can source locally. Getting all the ingredients for the Clay Substrate will be difficult and quite expensive too as I need quite a lot. Same with ABG mix. 

In my job I work with soils and soil mixtures for planting outdoors and I can source horticultural pumice locally. It comes in different granule sizes but the one I'm interested in is 2-8mm. 

What I was thinking was to use 100% pumice covered in a thick layer of leaf litter. 

Below is an extract from the datasheet (in Swedish but most of it is in Science so you will probably get the most of it). Worth noticing is the porosity (85%). At a layer depth of 10cm 45% of the total substrate volume holds water while 40% is filled with air. This is why pumice in general is considered such a good additive to especially load bearing soils as it doesn't compact, has good drainage while still holding a lot of plant available water and oxygen. 

In this case the low weight will be a not so small advantage too. It's weight at field capacity is 85% of equal volume of water.

I'm thinking that this could be a quite good substrate but would be happy with some input from some more experienced viv operators. Maybe it could be beneficial to add something else into the mix? Charcoal?


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## Grimsrude (Apr 6, 2017)

Sounds interesting - I know people with planted tanks use pumice (boiled until it sinks) as a substrate additive or as full stone for decorative/plant-able landscaping. So it works well with aquatic plants, but I'm curious what sorts of plants, micro-fauna, and animals you'd be housing in the tank later? 

To be fair, what would be the difference between that and something like ... NEHERP LDL NEHERP - Substrates For Live Vivariums ... which I'm 90% convinced is just Growstone GS-1 Hydroponic Substrate | Growstone as, having the stuff, they both look the same and float, hold water, similar weight etc. I wouldn't be surprised to find all of these are just crumbled pumice stone lol.

EDIT: After a quick re-reading, both the NEHERP stuff and growstone are made from recycled glass. So they are in fact not pumice, but meant to replace it.


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## OllieNZ (Apr 6, 2012)

Are you able to get hold of moler clay or akadama?


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## Kalle (May 14, 2010)

Grimsrude said:


> Sounds interesting - I know people with planted tanks use pumice (boiled until it sinks) as a substrate additive or as full stone for decorative/plant-able landscaping. So it works well with aquatic plants, but I'm curious what sorts of plants, micro-fauna, and animals you'd be housing in the tank later?
> 
> To be fair, what would be the difference between that and something like ... NEHERP LDL NEHERP - Substrates For Live Vivariums ... which I'm 90% convinced is just Growstone GS-1 Hydroponic Substrate | Growstone as, having the stuff, they both look the same and float, hold water, similar weight etc. I wouldn't be surprised to find all of these are just crumbled pumice stone lol.
> 
> EDIT: After a quick re-reading, both the NEHERP stuff and growstone are made from recycled glass. So they are in fact not pumice, but meant to replace it.


I know they use foam glass (from recycled glass) for road construction too, when you need a very light material due to soggy boggy conditions. It is similar to pumice though I haven't found any comparable data sheets. But it's basically made the same way so the qualities should be similar. Hasopor is a big producer of foam glass, at least in Europe, and it looks very similar to pumice. 

As a substrate (by my reasoning) pumice would itself be inert, just supplying structure, surface area and pores for both water and air to be contained while having good drainage. Together with leaf litter I would think that it could sustain micro fauna quite well while also be a good substrate for plants to grow in. 

I know they plant trees in 100% pumice in urban areas where the soil has to be load carrying and covered by stone or asphalt. It's there that I got in contact with it. Traditionally you would use big granule sizes and load the big pores between them with organics for nutrients but now some people are just using pure pumice (or normal crushed rocks) and let time fill it up with nutrients and organic material. As the pumice stones forms sort of a skeleton that can't be compacted the stuff between won't be compacted either by trampling or other loads. That's the theory behind "structural soil" or "load bearing soil". For it to work the rocks has to be in contact with each other and the organic soil can't be more than the volume of empty air between the rocks. In normal macadam or sorted gravel that's about 30%. In one cubic meter (1000l) of gravel you can fit 300l of soil. You can either flush the soil down with water or you can mix it dry before hand and then lay it out. 

Now I'm basically thinking out loud but what if you took larger sized pumice and mixed it with 30% of granulated clay substrate? In theory you would get a load bearing soil with high clay content that's not very sensitive to compaction or disturbance.


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## Kalle (May 14, 2010)

OllieNZ said:


> Are you able to get hold of moler clay or akadama?


I might, and it seems to be similar to pumice right?


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## OllieNZ (Apr 6, 2012)

Kalle said:


> I might, and it seems to be similar to pumice right?


No, it's a baked clay. Reddish in colour has a high cation exchange capacity, it's pretty stable and not too heavy. I've used it for planted aquaria in the past and going to be using it for my upcoming viv.
If I recall correctly pumice is inert.


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## Kalle (May 14, 2010)

OllieNZ said:


> No, it's a baked clay. Reddish in colour has a high cation exchange capacity, it's pretty stable and not too heavy. I've used it for planted aquaria in the past and going to be using it for my upcoming viv.
> If I recall correctly pumice is inert.


But Akadama seems to be mined. 

I read this on it's wiki:
"While akadama is more costly than alternative soil components, it is prized by many growers for its ability to retain water and nutrients while still providing porosity and free drainage. For all of its qualities, many bonsai growers consider the cost of akadama prohibitive or unnecessary. Still other growers claim that when subjected to cold and wet climates, the granules progressively break down into smaller particles which inhibit drainage, an essential characteristic of bonsai soil." 

By just reading this and having no first hand knowledge about Akadama it seems that pumice would have all the good qualities specified while having none of the bad ones (breaking down over time).


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## Kalle (May 14, 2010)

What clay based soils have that pumice doesn't, is high cation exchange capacity. There's no colloids in pumice. That's why I was thinking that perhaps adding say 30% of another clay based soil could be beneficial while still keeping the structural integrity of the pumice (and the soil itself) intact.


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## Kalle (May 14, 2010)

A pic of how a structural soil is constructed. There's no cars driving inside our vivariums but compaction can still be a problem. Maybe a soil skeleton can help with that?









Image source: Urban Horticulture Institute, Horticulture Section, School of Integrative Plant Science, Cornell University


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## OllieNZ (Apr 6, 2012)

It would seem akadama is available in various grades of hardness, I was under the impression that the hard grade was baked to attain the hardness. Moler clay is similar but not identical to the akadama but they are used interchangeably.


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## Kalle (May 14, 2010)

OllieNZ said:


> It would seem akadama is available in various grades of hardness, I was under the impression that the hard grade was baked to attain the hardness. Moler clay is similar but not identical to the akadama but they are used interchangeably.


Yes, that's what I figured too after reading about them. Seems like it could be a good choice for vivaria.


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## OllieNZ (Apr 6, 2012)

Kalle said:


> Yes, that's what I figured too after reading about them. Seems like it could be a good choice for vivaria.


You could also 'enrich' it by soaking it in calcium rich water.


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## Kalle (May 14, 2010)

OllieNZ said:


> You could also 'enrich' it by soaking it in calcium rich water.


Do you plan to use it straight or in a mix?


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## OllieNZ (Apr 6, 2012)

Kalle said:


> Do you plan to use it straight or in a mix?


Straight, topped with leaf litter just to keep it simple. I will be drilling the bottom and installing a bulkhead for drainage.


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## Kalle (May 14, 2010)

OllieNZ said:


> Straight, topped with leaf litter just to keep it simple. I will be drilling the bottom and installing a bulkhead for drainage.


That is what I have planned as well. Propably a slightly raised false bottom (10mm maybe) but I'd rather have a couple of extra inches of soil than a water/air reservoir in the tank.


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## OllieNZ (Apr 6, 2012)

Kalle said:


> That is what I have planned as well. Propably a slightly raised false bottom (10mm maybe) but I'd rather have a couple of extra inches of soil than a water/air reservoir in the tank.


I was just planning on covering the drain with mesh, no false bottom. The 3-8mm grain size I've purchased should give plenty of drainage.


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## Pumilo (Sep 4, 2010)

My daughter and I dipped a toe into the Bonsai hobby for a while. Yes, akadama is mined, and it is clay. The hardness grading comes from how deep it is, with lighter grades being mined from the top. The deeper you go, the harder it gets.

Akadama is used in Bonzai to be well drained, porous, and last a long time. I don't remember for sure, but it may also supply minerals. Another property it usually has, is a high price tag. Lower grades are less expensive, but they are not as hard, and thus, not as long lasting. Keep in mind that in Bonzai, you replant your tree every year, giving it's roots a good haircut, and putting it into new, fresh akadama mixture. That tells us that in the bonzai hobby, akadama is only used for a year, then thrown out. As far as we know, it hasn't been tested much in the hobby, but in my opinion, it would make a great substrate, but why, when there is turface you could use?

Have you looked at Turface? It makes an excellent stand-alone substrate. Turface is a man made clay. It is fully fired and rock hard. Selecting a grade similar in size to kitty litter will give you good drainage, will be nice and porous, and will last virtually forever. It will certainly outlast your frogs. Another property it usually has, is being dirt cheap. We already know that it has been well tested in the hobby. I have always used the All Sport Pro grade, purchased at a John Deere Landscape Supply.

My only concern with pumice would be that it is also an industrial abrasive. I don't know if that would present a problem or not.

I personally don't like the idea of trying to enrich a hardened clay by spraying it down with calcium water.
Did you know that too much calcium is every bit as bad as not enough? Are you aware that hypercalcemea can be fatal? Did you know that too much calcium can actually weaken your bones?
What are your controls over spraying with calcium? How much do you use for how much substrate? What keeps it from releasing too much calcium at once? How often do you respray, and do you respray a full dose, or do you rely on some still being at the top surface? 

In any good calcium bearing clay substrate, the amounts of calcium we use are not just pulled out of...somewhere. Clay substrates started with Matt Mirabello bringing home samples of rainforest clays, and having them analyzed in a lab. We had a starting point to aim for, and it was fully natural, like what they see in the wild. The calcium in my substrate, and in the substrates that based mine on, are buffered, so to speak. The calcium is spread throughout the clay, imbedded in it. It can't wash away and leave you with no calcium, because the clay extremely slowly wears away with repeated misting cycles, exposing more clay and more calcium. It always gives micro doses.
What you are proposing with spraying it down could be really bad. Yours would be mostly surface coated, and always moist. Those are not conditions leading to always giving a micro dose. Doses would be very erratic, being strong when you first applied, possibly to the point of toxicity, and getting weaker with repeated misting cycles. These conditions are more likely to overdose at first, then be not enough.

There are already quality supplements out there. Use the traditional methods of dusting your flies. I have never had any problems using Repashy products for my frogs.

There is no shortcut to a calcium bearing clay substrate, save paying someone to make it for you. With clay substrates you've got to go all in, or go a different direction. If you go in a different direction, I promise you that Repashy has put plenty of research into how to supplement properly.


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## Kalle (May 14, 2010)

@Pumilo
I have been checking out Turface but I can't seem to find any product that resembles it here in Sweden. As it is fired, does that mean that it is inert and the actual chemical composition isn't that important? Because I can maybe find some fired clay granules of a good size, but it probably won't match the clay that Turface is made from.


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## OllieNZ (Apr 6, 2012)

I've not been able to find a source of turface either.
A bit more info on Moler Clay (it seems terramol is a common commercial name)
Terramol
Diatomite & Moler Insulation - Material Properties | Skamol

I wasn't suggesting using the enriched clay (in this instance) as a replacement for correct supplements. Just putting something there so its generally available to micro fauna etc. Treating it as a totally inert substrate with no chemical benefit would be a simpler way of looking at it but it will still try to fill it's cation exchange sites over time.


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## Pumilo (Sep 4, 2010)

Kalle said:


> @Pumilo
> I have been checking out Turface but I can't seem to find any product that resembles it here in Sweden. As it is fired, does that mean that it is inert and the actual chemical composition isn't that important? Because I can maybe find some fired clay granules of a good size, but it probably won't match the clay that Turface is made from.


While turface may slowly release minerals, the amount would be minute, as any breakdown would be extremely slow.
So, yes, you should consider turface inert. In theory, you could have a potter fully fire a batch of kitty litter for you, and that would work. We are however, talking fully fired. Kitty litter is sodium bentonite, which absorbs water like crazy, and can quickly turn to mush, especially as a substrate rather than on the walls. Haha, my first substrate recipes were heavily sodium bentonite based, and were complete failures. They didn't last more than a couple months. Well, I guess they led to success, so maybe not complete failures.
Anyway, yes, if you can find something similar that is fully fired, the type of clay used shouldn't be crucial to good performance. If not fully fired, composition becomes much more important, as you have to balance being soft enough to release calcium the same way the rainforest floor does, with being firm enough to last for years.


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## backafter20 (Mar 11, 2011)

Great to hear a thumbs-up for turface, as that is what I used in my first two vivs. I got it for under $20 for a 50lb bag at a landscape supply company. I added crushed leaves, charcoal, a bit of ground coconut coir and fine fir bark as well, but it's still 80% or so turface. Seems to be working so far, but since it's only been one week, it isn't much of a testimony. Good luck to you Kalle, in finding something similar.


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## Kalle (May 14, 2010)

Pumilo said:


> While turface may slowly release minerals, the amount would be minute, as any breakdown would be extremely slow.
> So, yes, you should consider turface inert. In theory, you could have a potter fully fire a batch of kitty litter for you, and that would work. We are however, talking fully fired. Kitty litter is sodium bentonite, which absorbs water like crazy, and can quickly turn to mush, especially as a substrate rather than on the walls. Haha, my first substrate recipes were heavily sodium bentonite based, and were complete failures. They didn't last more than a couple months. Well, I guess they led to success, so maybe not complete failures.
> Anyway, yes, if you can find something similar that is fully fired, the type of clay used shouldn't be crucial to good performance. If not fully fired, composition becomes much more important, as you have to balance being soft enough to release calcium the same way the rainforest floor does, with being firm enough to last for years.


Thanks for the info! I'll see what I can find. I might even try to fire it myself. A case of beer and a big fire on a summer night is always nice. 😊


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## Kalle (May 14, 2010)

backafter20 said:


> Great to hear a thumbs-up for turface, as that is what I used in my first two vivs. I got it for under $20 for a 50lb bag at a landscape supply company. I added crushed leaves, charcoal, a bit of ground coconut coir and fine fir bark as well, but it's still 80% or so turface. Seems to be working so far, but since it's only been one week, it isn't much of a testimony. Good luck to you Kalle, in finding something similar.


That mix sounds a bit like options that I've been thinking about too. Glad to hear that it's working out so far!


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## Pumilo (Sep 4, 2010)

backafter20 said:


> Great to hear a thumbs-up for turface, as that is what I used in my first two vivs. I got it for under $20 for a 50lb bag at a landscape supply company. I added crushed leaves, charcoal, a bit of ground coconut coir and fine fir bark as well, but it's still 80% or so turface. Seems to be working so far, but since it's only been one week, it isn't much of a testimony. Good luck to you Kalle, in finding something similar.


That should work well for a long time.

Kalle, look up firing temperatures first. I believe they are sky high, and require a firing oven, or a bit of imagination. I think you can pull it off with a pit method at home. You'd have to look up how it's done. 
I know it can't be done in a home oven.


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## Kalle (May 14, 2010)

Pumilo said:


> That should work well for a long time.
> 
> Kalle, look up firing temperatures first. I believe they are sky high, and require a firing oven, or a bit of imagination. I think you can pull it off with a pit method at home. You'd have to look up how it's done.
> I know it can't be done in a home oven.


I've actually been looking into it, most because I've been wanting to try to fire some traditional/paleo pottery. Two methods are commonly used, oxidizing and reducing. In the first one the clay is just put straight into a big fire and in the other one the clay is covered up and a fire is burned around it, causing an anaerobic environment. Much like when you make charcoal. 

The super high temperatures are needed if you need the clay to sinter and become waterproof. At lower temperatures it will become hard and won't soften by water but it will absorb it. 

I've seen videos of people making really nice pottery in an old oil drum that's been loaded with firewood. You fire it hard and then let it cool slowly. 

Another product I've been looking into is "grog" (had to google the English term). It's fired and ground up clay, used in pottery clay to strengthen it and give it a rustic look. Comes in different sizes but most have quite small particles. Like 0.5-2mm was the biggest I could find. But it wasn't that expensive.

https://en.m.wikipedia.org/wiki/Grog_(clay)


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