Backyard Aquaponics
A place to discuss aquaponics

careful most steel wool has soap impregnated

this is true the pink gives it away

you can find the plain stuff though

ahhhh the pink bits

Steel wook has 2 main types: The "pink" stuff - for scrubbing dishes - loaded with soaps, and the stuff used in shops - may have oils and machine shop residues. The latter would be preferable to soaps, (since soaps can kill fish), but you may still want to rinse it out to get rid of any oils. The best stuff would probably be the old, rusty steel wool you find in Dad's old workshop - most of the oils or whatever would have had years to dissipate, and it would already be started on oxidization.

Oh boy, we're onto something now. I emailed the RSG (who is called Anthony, by the way), and told him how excited everyone was by the idea of anaerobic micro-environments. He's really in to bacteria, and I posed our question about getting the bacteria to break down iron for us. He wrote back:

Janet,
That's cool that everyone is intersted in the micro environment
thing. Rusty nails (ferric or Fe(III) iron, which is not very soluable in
water) in anoxic waters will definitely get reduced to ferrous (or Fe(II)
iron), which is water soluable and available to plants. It might be a good
idea to try. Let the bacteria in your system do the chelating for you!
Does anyone add charcoal to their systems? It is used in standard
fish tank filters, Britta filters for drinking water, etc. I'm not entirely
sure of all the chemistry that happens with charcoal, but in addition to
providing adsorption sites for cations (metals and ammonium) and hydrophobic
organic molecules (toxins), charcoal also catalyzes all sorts of
reduction/oxidation reactions and I'm willing to bet that the bacteria can
use it to facilitate denitrification, but that is really just a wild hunch.
As for denitrification, I don't think you have a lot going on in
your system, given your huge nitrate concentrations and the fact that you
use pebbles. We might want to brainstorm about how to enhance anerobic
microzones. Perhaps a few vertical columns (2-3" pvc tubes or wire
cylinders) filled with sand might help. You would need a carbon source to
this sand column to create an oxygen demand. Perhaps you could have your
inflow water always draining into the top of this pvc tube. This way, the
freshest fish fecal material is continuously pushed through the sand, the
sand is always saturated to the top (don't want reaeration) and the water is
always flowing in one direction (from top to bottom, although with variable
speeds depending on the water level in the rest of the tank/bed). All of
this would promote a denitrifier community to develop. Try it in one bed
tank and see if the nitrate coming out of that tank is lower than the others
(it might take a week or two for the bacterial community to get into gear).
Also, you would not want these tubes to be right near the drain so that the
bacteria in the aerated bed would have time to oxidize all that ugly
smelling anaerobic stuff. Regardless, the water getting to the fish will
get plenty of aeration by droping into their tank.


Just thoughts. Its fun to think about.
Anthony

Oh, and this was my original inquiry to him:

I posted what I learned from you on our Aquaponics forum.
Everyone is very excited about the idea of anaerobic micro-environments.
Then it got more exciting when someone pointed out that there is bacteria
that will transition iron in an anaerobic environment, such that our plants
might be able to take it up. We also think that we would have to run a lower
nitrate setup to get this to happen. Is it reasonable to think that some
rusty nails at the bottom of the growbed would get colonized by
iron-reducing bacteria and provide some/all of the iron needs for the
plants?

fun fun fun

personally i dont thnk that we should promote tooooo much anerobic(ness)

the small areas that have become clear now i think would do nicely. Remember, nitrate reduction is not a goal, thats what the plants are for.

RE: the steel wool, you can find some at the stores that is just plain stuff, not oiled or soaped up. though boiling it in some water certainly wouldn't hurt.

See what i was saying about the abundance of beasties that help out that we don't know about? While i'm absolutely tickled pink to learn about them we need to remember that they do exist and are hard at work, weather we have quantified them or not.

Steve

Anthony saw my system when the nitrates were pretty high. I had just dumped the cleanings from 2 aquariums in, plus pulled out my green beans to make way for the next planting. I think that's why he spent more time on that. I've emailed him back to see what his ideas are to get the iron thing going.

Seems that from what he is saying, and from what I have seen, we will develop some anaerobic microenvironments especially in the bottom corners of the GBs away from the drains and inlets. Sand and silt tend to accumulate in the bottom and corners, and if that's where you put the boiled steel wool and maybe some charcoal (crushed), you should get the stuff he's talking about, especially if your water never drains below the last 5mm.

More thoughts....

Shouldn't be difficult to get the anaerobic microenvironments while keeping a predominately aerobic environment....

Thanks again JP, i was getting a little bored and was ever so curious on why i have never put iron chelate into my system

I guess than another one for the gravel camp...............(not that i'm keeping score )

You can get safe steel wool at a wood working store. It is used to buff finishes to a high gloss and will contain no additives.

I wrote to Anthony:
My major denitrification mechanism is intended to be the plants.
There are folks who have systems that run at 0 nitrates, yet have lush
growth. Their plants are pulling the nitrates out of the system as fast as
it comes available. My nitrates were at 10ppm about a month ago, but then I
dumped in 40gal worth of aquarium cleanings.
Then I tore out the green beans to make way for the soybeans. Even though I
had to do an emergency 50% water change to get rid of the kelp tea problem,
I have not compensated for the huge influx of nitrates plus the reduction in
plant mass. The nitrates are not causing a problem, but it gives a false
read on how I think the system should run.


So I'd be more interested in creating an anaerobic environment for the iron
rather than for the nitrate. The bottom few inches of each bed are
continually wet, but really hard to get to. Your idea of vertical PVC pipes
sounds good. I could sink a 4" pipe vertically underneath the water
distribution line. (It has to be big enough to get my hand into so I can dig
the gravel out from the inside.) If I drilled a few holes around each end of
the pipe, then water could flow in the top, and out the bottom holes. Excess
water would overflow through the holes that the top. Should I fill it with
rust, sand and carbon? Or leave out the carbon? What are your thoughts to
get the iron action going?


--Janet.
-------------------------------
Anthony replied:

Hi Janet,
Your plan with the 4" pipe sounds great. I would fill it with sand
and nails (if the nails are new, wash with detergent to remove any oils).
The carbon (for biological oxygen demand) will come from the water pumped in
from the top. Activated charcoal on the other hand probably wouldn't hurt.
By the way, denitrification refers specifically to the conversion of
nitrate to N2 gas. The plants are simply doing what is called biological
uptake. For you to get good nitrate removal by plants, not only do they
need to be growing lush and fast, but you need to remove the plant material
(harvest, weed, prune, etc.). If dead leaves fell back into your bed and
decayed, the nitrogen would just return to the water and get reconverted to
nitrate.


Anthony

-----------------------------

Fun fun fun! There's sand in the kids' sandbox, a bunch of activated charcoal in my supply drawer, and rusty washers and springs lying about. All I need is a foot of 4" PVC.

Very intresting stuff. I guess for good fish health the target nitrate reading should be 0. Add more growbeds, more plants, plants that utilize more nitrates, or add an anaerobic sand filter. Is that about right?

Well, it sounds like the taste of the fish is improved by lower nitrates--from Monya's bathtub purging experiment. I don't think the fish themselves care whether the nitrate is 0 or 100. However, to get the anaerobic iron action, we think we need lower nitrates.

Anthony's first anaerobic sand filter was to reduce nitrates by getting the bacteria to offgas it into N2O and N2. However, if you have iron in your anaerobic filter, and lower nitrates anyway, then the iron should be broken down into soluable form by the bacteria.

For fun, I'm going to go ahead and sink a 4 inch PVC pipe so I can get to the bottom of my grow bed. I'll just start with a couple inches of sand/nails/activated charcoal, and back fill the rest of the pipe with gravel. I guess I need an iron test, too. Or maybe I'll just watch the cabbage.

Steveand ange are currntly running their system at around 2.5ppm, and i'm more than happy with the growth!

I'd say just watch the cabbage