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

[Harold Sukhbir]

We have to bear in mind there are many studies done on both ocean fish and different conditions existing there and also on aquaculture but relatively little in AP conditions. In aquaculture, water is exchanged and changed periodically while in oceans conditions we have a massive body of water and complex ecosystems. In AP the loop is closed as far as metals go and i am concerned with the long term exposure of these in an AP recirculating system. I haven't found, this far, any studies on metals buildup in plant or fish with long term exposure to macro and micro nutrients and the effects, if any at all. I think, due to the nature of AP, it will be more prone to accumulation, especially in fish as compared to their presence in other settings.

TCLynx said:

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.

[TCLynx]

I go Boris's Mercury Check  from FilterWater.com and checked my system water with it (seeing as I have probably half a yard of red lava rock)

Well according to the test strip (which I believe is meant for testing drinking water) the reading came back 0.0  The next increment up on the test chart is 0.002 and that level is the EPA MCL (which I think means according to the EPA any level above that would not be safe for drinking water.)

 

How accurate these strips are, I can't say as I don't have any mercury contaminated water with which to check the calibration.

[Harold Sukhbir]

Great effort TC.It's a start, at least we know where we stand with Mercury in water. We really need some in-depth study or some Kobus type to help with methyl testing in our fish as the magnification can be exponential. Its possible to have a low reading of mercury in our water and at the same time high levels of methylmercury in our fish.

 

This is a quote from a passage in WIKI on methylmercury;

"The concentration of methylmercury in the top level aquatic predators can reach a level a million times higher than the level in the water."

To view the article

http://en.wikipedia.org/wiki/Methylmercury

I go Boris's Mercury Check  from FilterWater.com and checked my system water with it (seeing as I have probably half a yard of red lava rock)

Well according to the test strip (which I believe is meant for testing drinking water) the reading came back 0.0  The next increment up on the test chart is 0.002 and that level is the EPA MCL (which I think means according to the EPA any level above that would not be safe for drinking water.)

 

How accurate these strips are, I can't say as I don't have any mercury contaminated water with which to check the calibration.

[TCLynx]

next step might be testing the feed

 

[Harold Sukhbir]

Testing the feed may only show us that the mercury is within acceptable limits for humans. If it contains fish meal, mercury will be present. Exactly what happens when it is introduced to recirculating Ap systems and compounded by daily feeding over time, is unclear up till now. Our plants will use the macro's as needed and leave the rest to bacteria, algae, and fish, and in this aquatic chain my concern is mercury becoming methylated and magnified. Not many studies have been done in aquaculture on this, i think because both fish and water are turned over in a relatively short time frame(approx seven months) but in the case of AP we need to go more indepth with this to find out if accumulation is indeed taking place.

TCLynx said:

next step might be testing the feed

 

[Joseph Orlando]

OK!  I just talked to a geologist and here is the scoop I got from him.  Lava comes in two forms.  One is Basalt which usually occurs in eruptions underwater but can be part of a flow.  Basalt is dense and will contain heavy metals like Mercury.  However, Red Lava Rock, is considered a pumice, and is usually spewed from the volcano into the air due to itls light weight and should contain no heavey metals.  It seems it has to do with how the lava accumulates in the dome of the volcano.  So, Red Lava Rock should contain no Mercury.  This is good news to me.  I have been researching and trying to come up with a process for making expanded clay for my growbeds.  I'm close, but time, energy and money still has it cheaper to buy than produce.  Almost everything else available around here seems to be limestone and it is killing my ph ballance.  I bought 12 tons of the grey gravel that looks identical to the stuff that Murray Hallum is using just to find out it too is limestone.  Murray's gravel must be something different because I've been cycling for centuries and still can't get below an 8.0 ph.  SO....on to red lava rock.

TCLynx said:

I go Boris's Mercury Check  from FilterWater.com and checked my system water with it (seeing as I have probably half a yard of red lava rock)

Well according to the test strip (which I believe is meant for testing drinking water) the reading came back 0.0  The next increment up on the test chart is 0.002 and that level is the EPA MCL (which I think means according to the EPA any level above that would not be safe for drinking water.)

 

How accurate these strips are, I can't say as I don't have any mercury contaminated water with which to check the calibration.

[TCLynx]

I've used lots of red lava rock in the bottoms of grow beds and in ornamental pond filters.

 

I think Murray's rock could be what the Aussies call blue metal which I believe is crushed granite.  What the Aussies call scoria is what we usually call red lava rock.

 

Beware the pea gravel because that only describes size/shape.  Most pea gravel and the cheapest gravel found around here in Florida is going to be limestone of one sort or another.  (By the way, marble is just limestone hard enough to take a polish so not good for AP either.) 

 

Before spending lots of money on gravel, ask what type of rock it is.  Stuff like granite, and quartz type rocks are generally inert as it relates to pH and lava rock or scoria are generally good too though I've heard of some people having a high pH from clay dust on scoria before but that eventually went away.

 

If people don't know the type of rock, I usually suggest getting some samples and running some tests.  Like rinsing the gravel well and then putting it in a cup of vinegar, if it fizzes and foams big time like the kids baking soda and vinegar volcano, you probably don't want to use it in AP.  Even if it just fizzes a lot, you probably don't want to use it.

 

You can also take some of the washed gravel and soak it in distilled water for a week or so and see if the pH goes up.  Beware false pH readings from tap water just drawn (my water comes from the faucet at 7.0 but that is a false low reading because of CO2 trapped in the water from the well.  If I outgass the CO2 for a day the real reading of my tap water will be over 8.  Now the nitrification process is enough to bring my highly buffered tap water back down but it will never manage if the grow beds are full of limestone too.) 

 

My big system has taken 2 years to get below the buffer level 7.6 of the shells it is full of and it only falls below that when the fish are feeding full tilt through warm weather and that usually doesn't fall below 7.0-7.2, now that it is cooler the pH is back up between 7.2 and 7.6.

 

The cheapest gravel that works well for Aquaponics around here (central Florida) is the 1/2" brown river rock.  It is mostly quartz type river pebbles.  Perhaps a bit on the small side for aquaponic purposes and it is heavy but it washes off pretty easily and isn't too hard on the hands for planting.  It looks pretty nice too.

 

I'm terribly sorry to hear that you got such a huge load of limestone gravel Joseph.

[Joseph Orlando]

TCLynx, Thanks... 

Fortunately, I can use the rock I bought to level my tanks and greenhouse.  It will also serve as drainage if there is a spill or leak under the tanks.

Just got a load of Red Lava Rock.  I'm in the process of washing it now.  The porosity should be great for maintaining bacteria levels.  I still would like to have something heavier in there for taller plants like tomatoes so they don't uproot out of lighter medium.

 

JoeJ

TCLynx said:

I've used lots of red lava rock in the bottoms of grow beds and in ornamental pond filters.

 

I think Murray's rock could be what the Aussies call blue metal which I believe is crushed granite.  What the Aussies call scoria is what we usually call red lava rock.

 

Beware the pea gravel because that only describes size/shape.  Most pea gravel and the cheapest gravel found around here in Florida is going to be limestone of one sort or another.  (By the way, marble is just limestone hard enough to take a polish so not good for AP either.) 

 

Before spending lots of money on gravel, ask what type of rock it is.  Stuff like granite, and quartz type rocks are generally inert as it relates to pH and lava rock or scoria are generally good too though I've heard of some people having a high pH from clay dust on scoria before but that eventually went away.

 

If people don't know the type of rock, I usually suggest getting some samples and running some tests.  Like rinsing the gravel well and then putting it in a cup of vinegar, if it fizzes and foams big time like the kids baking soda and vinegar volcano, you probably don't want to use it in AP.  Even if it just fizzes a lot, you probably don't want to use it.

 

You can also take some of the washed gravel and soak it in distilled water for a week or so and see if the pH goes up.  Beware false pH readings from tap water just drawn (my water comes from the faucet at 7.0 but that is a false low reading because of CO2 trapped in the water from the well.  If I outgass the CO2 for a day the real reading of my tap water will be over 8.  Now the nitrification process is enough to bring my highly buffered tap water back down but it will never manage if the grow beds are full of limestone too.) 

 

My big system has taken 2 years to get below the buffer level 7.6 of the shells it is full of and it only falls below that when the fish are feeding full tilt through warm weather and that usually doesn't fall below 7.0-7.2, now that it is cooler the pH is back up between 7.2 and 7.6.

 

The cheapest gravel that works well for Aquaponics around here (central Florida) is the 1/2" brown river rock.  It is mostly quartz type river pebbles.  Perhaps a bit on the small side for aquaponic purposes and it is heavy but it washes off pretty easily and isn't too hard on the hands for planting.  It looks pretty nice too.

 

I'm terribly sorry to hear that you got such a huge load of limestone gravel Joseph.

[TCLynx]

I like the positive attitude.  And it will be a handy source of limestone to put in a buffer bag to hang in the tank if you need to buffer pH up at a later date.

 

I think you will find that the lava rock once well saturated will be heavy enough to anchor things like tomatoes if you are also staking or tying them up.  Corn or really big freestanding things (banana or papaya) are the only things I would worry the hydroton wouldn't support but I think you will find the lava rock is irregular enough and heavy enough to anchor the roots pretty well, perhaps too well.

 

Biggest drawbacks with lava rock are 1- is is really dusty and tedious to wash, must be gentle with it while washing too. and 2- it can be hard on the fingernails when digging in it.  But I think you will be fine.

 

Joseph Orlando said:

TCLynx, Thanks... 

Fortunately, I can use the rock I bought to level my tanks and greenhouse.  It will also serve as drainage if there is a spill or leak under the tanks.

Just got a load of Red Lava Rock.  I'm in the process of washing it now.  The porosity should be great for maintaining bacteria levels.  I still would like to have something heavier in there for taller plants like tomatoes so they don't uproot out of lighter medium.

 

JoeJ