Using Pumice

[miko]

hallo
Glad to join this forum. Can anyone explain the use of pumice for  grow beds media.
Because right now I use it on the advice of some friends. Are there any
special techniques.
thanks

[Sylvia Bernstein]

Hi Miko. I'm assuming you are talking about lava rock. Should work well, although I've never used it so I'm hoping some others (especially you Hawaiians) will jump in here. As long as you stick to the usual precautions about aiming for a 3/4" size I wouldn't think lava would have a pH buffering problem. And the image you attached shows a nice smooth surface so it should also have the side benefits of being easy on the hands, as well as light weight and porous. I'd say to go for it, but, again, I've never used it so I'd wait to see if someone who has jumps in here.

[TCLynx]

The important things about choosing growbed media is to get something big enough to allow for good drainage and less clogging while still being small enough to hold plants and hold some moisture. Also, you want media that won't affect your pH directly. (Limestone and marble will keep the system pH too high for most plants to be very happy.)

I would expect pumice to make good media but I've never handled it myself so I don't really know the particulars for that media. I expect washing it to be pretty important and I also think it may be a bit fragile so you probably need a fairly gentle method for washing (tumbling in a cement mixer might not be a good choice here.)

I use 1/2" river rock for my media but I often use larger lava rock right around the base of the gravel guards around my drains.

[miko]

Thank you for your suggestions both, Sylvia and TCLynx. It is true that I use a stone lava rock. At my place is quite cheap compared with Hydroton. I also have to test the ph of the water and showing the figure 7.0. Water from growbed to feed approximately 100 tail catfish. But this new process I run about three weeks. I have not made the growth rate of the fish. Similarly, eggplant plants, still in growth phase. Not yet bear fruit. Once again thanks for the advice. I will report the progress of my experiment on this forum.

[Joseph Orlando]

I haven't used lava rock either, however, being so light it seems it might be a problem with heavier, taller plants like tomatoes.  Not enough umphhh to keep the plant from up-rooting and falling over.  I think Murray mentioned that as a downside to expanded clay.

Sylvia Bernstein said:

Hi Miko. I'm assuming you are talking about lava rock. Should work well, although I've never used it so I'm hoping some others (especially you Hawaiians) will jump in here. As long as you stick to the usual precautions about aiming for a 3/4" size I wouldn't think lava would have a pH buffering problem. And the image you attached shows a nice smooth surface so it should also have the side benefits of being easy on the hands, as well as light weight and porous. I'd say to go for it, but, again, I've never used it so I'd wait to see if someone who has jumps in here.

[Harold Sukhbir]

Of course i am not a scientist by any means but recently was doing some reading about mercury and found quite a lot of info on the subject. It seems that volcanoes emissions and volcanic rock contains elemental mercury. In its natural form it is relatively harmless to humans. When it finds a water source it is absorbed by bacteria then plankton then fish then US! The form becomes methylated into methylmercury and becomes increasingly concentrated as it goes up the food chain and can present to humans in toxic levels.In Ap we have an ecosystem similar to that in nature and i am concerned with the impact if a source of elemental mercury was introduced.  I have copies of studies done on the subject but are mostly in-depth and probably not suited for this occasion, however i've selected a more concise article on this for you reading;

 

http://www.oregon.gov/DHS/ph/envtox/fishfact.shtml.

[TCLynx]

Hum, there are many of our friends down in OZ using scoria (red lava rock) and I probably have half a yard of it mixed into my systems.  Perhaps will have to run a mercury test.

[Harold Sukhbir]

If you can run that test would be great for all of us i'm dying to know( pun ). 

TCLynx said:

Hum, there are many of our friends down in OZ using scoria (red lava rock) and I probably have half a yard of it mixed into my systems.  Perhaps will have to run a mercury test.

[TCLynx]

I got a test kit on the way (it is only a drinking water test kit so I don't know if it will test for all kinds of mercury but will be curious to see what it tells us.)

Harold Sukhbir said:

If you can run that test would be great for all of us i'm dying to know( pun ). 

TCLynx said:

Hum, there are many of our friends down in OZ using scoria (red lava rock) and I probably have half a yard of it mixed into my systems.  Perhaps will have to run a mercury test.

[Harold Sukhbir]

Not all volcanic rock are contaminated with mercury or arsenic it depends on the particular geography and history of the location. At any rate you're better off knowing if indeed it's an issue to your own safety. Looking forward to your results(hope it's negative). Are you testing for methylmercury? or the element mercury alone?

TCLynx said:

I got a test kit on the way (it is only a drinking water test kit so I don't know if it will test for all kinds of mercury but will be curious to see what it tells us.)

Harold Sukhbir said:

If you can run that test would be great for all of us i'm dying to know( pun ). 

TCLynx said:

Hum, there are many of our friends down in OZ using scoria (red lava rock) and I probably have half a yard of it mixed into my systems.  Perhaps will have to run a mercury test.

[TCLynx]

I'm guessing the test only looks for inorganic mercury but I'm not certain.

 

[Harold Sukhbir]

Not much of a difference, once the metal is there it becomes absorbed by our bacteria then concentrated all the way up the chain.

[TCLynx]

I was doing a bit of reading and it seems that the bacteria most likely to convert it are going to be in anoxic or low oxygen conditions with sulfur present.  but in any case, ya don't really want Mercury to be concentrating at any levels in your food system.

Harold Sukhbir said:

Not much of a difference, once the metal is there it becomes absorbed by our bacteria then concentrated all the way up the chain.