# Lava Rock under Aquqtic Soil?



## Bobtastic (21 Sep 2010)

Hi all,

I was wondering if anyone has ever used broken/crushed lava rock underneath their chosen aquatic soil? I was thinking that lava rock is relatively similar to Power Sand but without the added organic matter.

Would adding it under the soil help the bacteria growth and water circulation in the substrate? Maybe it can absorb some nutrients and allow the to be access by the plants roots?

Sorry if this has been asked /answered b4.


----------



## ceg4048 (21 Sep 2010)

Hi Bob,
          That would be a waste of time and money. Powersand has very little to do with lava rock and they are not really used for the same purpose. Powersand is pumice soaked in very high concentration of NPK. In fact, the concentration is approximately 2 orders of magnitude higher than EI. Powersand does nothing special regarding sediment circulation, but it's extremely high nutrient concentration allows the plants to grow quickly, then the nutrients are leached out after a month or two and becomes basically inert.

If you want to add bacteria to the sediment, just go out into your garden or the nearest park and grab a handful of grass and a little soil, dry it out until brown and spread it out at the bottom of the sediment. There are plenty of bacteria outside for free. You don't need to pay cash money for germs. If you don't like the idea of grabbing a handful of strange dirt that may have dog doo-doo in it - which would definitely spoil your day, then just get a cupful of mulm or detritus from an existing filter or other tank and place it at the bottom of your chosen sediment (and place some in your new filter as well). That will have plenty of bacteria along with carbohydrates for them to feed on. If you have any peat a small amount can be used as lunch/supper for the bacteria. Within 6 weeks you'll have more bacteria than you ever dreamed of. As plant roots grow they oxygenate the sediment and provide for circulation. There is  no need for moon rock, or power rock, or rock from Mars. Keep it simple mate.  

Cheers,


----------



## ghostsword (22 Sep 2010)

I have tried old filter media crushed on a ice crusher, lots of bacteria and coarse enough for the bottom, especially if you cap it with sand. Why throw it away when we can recycle it, and it is very cheap.

Only drawback is that if you uproot plants some have roots going through the media.


----------



## Bobtastic (22 Sep 2010)

Is it not the Powersand Special that is "treated" with the Bacteria 100 and SuperClear? I'm a little confused then... Is there no benefit to introducing a course and porous layer under the soil?

I have a mature filter so I would be able to introduce some mulm quite easily. I also have some lava rock left over from a recent bbq purchase. But u say there would be no benefit to mixing the two under the aquatic soil?


----------



## flygja (22 Sep 2010)

OK now I'm feeling a bit daft for spending 2 hours to crush lava rock and layering it on the bottom of my tank


----------



## Bobtastic (22 Sep 2010)

Lol, I was told on here by others that Power Sand is just volcanic pumice. The difference presumable between Power Sand (PS) and Power Sand Special (PSS) is that PSS is infused/coated in Bacter 100 and Special Clear which you would have to buy and introduce separately with just regular PS. 

So if lava rock has the same or similar properties to volcanic pumice and you introduce an alternative bacteria source (namely filter mulm) with a food source would the effect not be similar? Is the the purpose of the pumice only to allow for a greater surface area for the bacteria? Does it not server any other purpose?


----------



## ceg4048 (22 Sep 2010)

Bobtastic said:
			
		

> Lol, I was told on here by others that Power Sand is just volcanic pumice. The difference presumable between Power Sand (PS) and Power Sand Special (PSS) is that PSS is infused/coated in Bacter 100 and Special Clear which you would have to buy and introduce separately with just regular PS.


Well that actually could be. I can't keep up with all the twists and turns of the product additions. But the key word here is "buy".



			
				Bobtastic said:
			
		

> So if lava rock has the same or similar properties to volcanic pumice and you introduce an alternative bacteria source (namely filter mulm) with a food source would the effect not be similar? Is the the purpose of the pumice only to allow for a greater surface area for the bacteria? Does it not server any other purpose?


Lava rock does not have the same physical properties as pumice since they are formed by different mechanisms. Lava (if it actually is lava and not just some marketing phrase) is formed by molten rock and is expelled from the planet core. It is expelled in a non-explosive manner so it maintains it's density but does trap gasses due to it's high viscosity. 

Pumice is formed during high energy explosive pyroclastic flow which has very high gaseous content. So pumice is more powdery, porous and is less dense. This porosity allows it to hold the soaked nutrients for a while, but then just as easily the nutrients leach out. Aquasoil is a clay which has NPK and peat baked on the surface, so it's nutrient retention is more long term. When used together the Powersand dumps loads of nutrients into the sediment giving a boost to the new plants. After it runs out of steam, perhaps a month or so, one still has high nutrient levels from the Aquasoil. I assume that it's about this time when the dosing program has you start pumping all the various N, P, or K liquids into the water column to keep growth rates from sagging.

In terms of sediment bacteria it doesn't matter that much what sediment you use because the nitrifying bacteria are limited to some extent by oxygen availability. This is different in a filter because you have a strong positive flow so that you can generate large populations and therefore surface area matters.

If I had the choice of filling the space occupied by the pumice or lava, I would just as soon have more Aquasoil or other clay filling that space, not pumice or lava, which are great for use as mulch in terrestrial plants because of their ability to trap moisture, and to block out the light to prevent weeds, but offer no significant advantage over clay or mud in an aquatic environment for that matter. 

Having said that, there is no big hit using them either, especially if you dose the water column.

All this stuff about sediment circulation is propaganda because there is no demonstrable advantage in efforts to increase circulation. This is why substrate heaters have disappeared from our collective consciousness because that's not how sediment dynamics work. 
1. When a plant photosynthesizes it sends oxygen from the leaf down to the roots and is expelled into the sediment. This causes circulation.
2. Hydraulic pressure gradients above due to water movement automatically have some impact on the fluid in the sediment below, so there is some movement within the sediment. 
3. High concentrations of compounds in the sediment cause movement out of the sediment (or the reverse) due to osmotic pressure. 
4. Plant roots also work by electrochemical gradients. What I mean by that is that electrically charged particles such as nutrients interact with the root hairs. The hairs have special chemicals called "Transporters" which target specific ions of interest. So for example there are Nitrate Transporters which are chemically attracted to the negatively charged NO3- ion. The constant movement of these charged particles into and out of the root cell walls creates a current and this is a form of circulation. 

So there is gaseous exchange, hydraulic effects, osmotic forces and electrical exchanges occurring between plant and sediment. That's why there is no need for the addition or promotion of circulation techniques - and that's why we don't see any differences in growth performance when using these tactics. For example, pumice does not have nearly as high a CEC as clay or playsand does, so whatever benefits you might get from circulation due to porous structure is negated by the poor performance of nutrients to be transported to the root hairs. Powersand, in whatever variant, should be considered a one way vehicle for delivering the cargo to the sediment and then it's job is over. The nutrient imbued clay sediment takes over for the long term, because clay has a high performance in nutrient ion exchange between itself and root hairs.

Again, it's just an opportunity to sell you something, and since it doesn't really hurt to use pumice or lava there's little chance that someone will note a decline and claim hogwash.

Aerobic bacteria require Oxygen, Carbohydrates and NPK to develop their poplations. Filter or sediment mulm contains bacteria and carbohydrates in the form of detritus. When you dose the water column or if added to the sediment then your colony has all it needs to develop. If your plants are healthy then oxygen is made available to the bacteria via the roots. Really, that's all you need, just the basics. If you want to spend money to get all this other stuff then fine, but there would be little benefit.

If you want to test the performance of the bacteria seeding products versus simple mulm or garden dirt then you'd set up an equal number of tanks, half  of which will have mulm. Take periodic samples of the sediment by counting bacteria with a microscope. Compare the time it takes to achieve a certain population density for each group of tanks. 

Cheers,


----------



## Bobtastic (22 Sep 2010)

Wow... that seems pretty conclusive!

So just filter mulm and AquaSoil for me than! Thank Clive!

Told Fly! All that wasted crushing time indeed!


----------

