Backyard Aquaponics
A place to discuss aquaponics

[quote="janetpelletier"]My system already doesn't fully empty. The drains from the GBs are on the sides because that was where Rubbermaid put them. Hence, the autosiphons kick off when there is still a bit of water left. While I wouldn't put sand 2 inches deep in the whole grow bed, I am willing to try 12 square inches for a total of 24 cubic inches. (OK, so I'm bored and I like to tinker.)[/quote
]Ah ah a nother one bored terrible when its running smooth

OK, having given this some thought, and with the spectre of hydrogen sulfide wafting about, I'm shifting the plan. I used my 4 inch PVC to help me shore up the walls and dig down to the bottom of one grow bed. On the very bottom of my growbed, I dumped in my rusty nails and a double handful of charcoal. The charcoal is actually fairly fine, but coarser than sand. Then I backfilled the hole with the crushed coral, clay pellets and river rock that I had dug out. I tried to put most of the coral and clay pellets back on the bottom where it had come from. I lifted the PVC back out, so I just have an area at the bottom of the bed with a concentration of iron and small pieces of charcoal. I should get lots of anaerobic micro-environments in the charcoal, but not a totally anaerobic area. I also saved aside a water sample to check as a baseline once I get an iron test kit.

As I think about it, the "chelated iron" that I have coming actually has a lot of other trace minerals, too. All I will get from my modified BIC is the iron. There's going to be a strong temptation to put the chelated iron in there, too. My experiment isn't going to end up being terribly scientific, I'm afraid. But haven't we all learned a lot?!?

I have been thinking about this concept for a while, and it occurred to me that instead of using a flow through chamber for anaerobic bacteria, a bio-digester type idea may be better. A batch process of fish wastes passed through it to decompose with iron shavings added. After a few weeks the water output water could be oxygenated and slowly added back to the AP system water.
Methane harvesting or proper venting is important here (someone resourceful could plumb it to a storage tank to use for cooking ), though with a smaller size it might not be an issue if outdoors. I realize this adds more processes than just adding iron chelate, but it does potentially bring it into the "Organic" realm even more-so.

It was this article posted recently that made me consider this:
http://www.fao.org/WAICENT/FAOINFO/AGRI ... /mandw.htm

I'm glad you're giving this some thought, Hayden. I don't have the ability to measure the results of what I did. I can tell you that it does not stink, but that I am sorely short on iron in the system. I have been supplementing with chelated iron.

If you have the room for scientific experiments, by all means, do it!

Well, after another stimulating day with the Really Smart Guy, his wife and kids at the beach, I've gone and done it. I built anaerobic sand columns into two of my grow beds. I sank 4-inch PVC vertically into the growbeds, dug out the gravel, and filled them up with sand (from the beach, of course) and a handful of charcoal. Water continually flows in from the top, and out the bottom. The sand never drains, regardless of the water level in the growbed. The hope is to get additional surface area and more anaerobic micro-environments to get rid of my excess nitrates. The anaerobic iron experiment is in the last growbed, and I can't tell whether it helps any, but I know it doesn't stink. I'm trying to reduce nitrates because after figuring out how to measure them a bit more accurately (by diluting the water sample with distilled water), I found that my nitrates were at about 1000. The fish never minded, but Holy Smokes!!! I've also been transplanting various plants into the system as fast as I can, so again, I won't be able to truely say whether the nitrates are going down because of the new sand columns or the Australian tree ferns. The sand columns have only been in place for a few days. I suspect they will need time to cycle up, just like any other aspect of the system.

Janet,

I have just found this thread and find it quite interesting. I have on several occasions found these type of anerobic areas in my presurized sand filters (believe or not). What happens is there is so much build up of solids that the filter begins to chanel, even on the back wash cycle, which ends up compounding the issue even more (and of course I get less filtering) I think that michael_Ferrini had said something to the effect of the channeling of the sand.

Anyway, I know for a fact it is heavy on the oxidation of metals.

I know the hydroponics folks as well as the regular swimming pool people seems to talk about this all being "bad".

I opened up my sand filter the on Friday to give it a clean and nearly all of the center of the filter had turned to this type of area, even with the high flow and realatively high pressures, I only had the outside 1 1/2 inches or so of the sand that was still actively filtering/passing the water.

So, all that said, I have been debating how I should incorporate this filter in to the scheme of the whole AP lay out. Steve and the others who have dealt with people who have swimming pools with large pressure sand filters my have interest in this.

My thought was this (tell me what you think of it based on you conversations with the RSG):

Flow the water out of the pool,
through the pump,
redirect it to the GB's,
then through the fingerling tanks,
then gravity feed back (probably only a portion of the overall flow)through the sand filter,
back to the pool.

This is not necessarily the perfect layout, however, it allows me to utilize everything in a beneficial way. I could easily bury a bit of FE in the sand filter.

The part I am so nicely surprised (though with the way God made everything else I guess there should be no surprise) about is that this "inherent problem" is that there are aspects of good in it to help keep everything else healthy.

Do you see any problems with what I am thinking?

I am glad to see this type of discussion, ESPECIALLY before I get it all plumbed together.

Mathew

Hi Mathew,
The only comment that I would have on your proposed arrangement is that the RSG felt it would be better if the water coming out of the anaerobic sand had a chance to re-oxygenate before being dumped back into the tank. So my sand filter is built in to the growbed, but as far away from the drain as possible. (In my case though, it is only about 15 inches.) This allows water to regain some oxygen (the fish would like that) and it allows some of the potential stench to dissipate/transform before is is released into the sunroom. So far, there is no stench to my nose, although soon, I expect that if I dug into the sand, I would detect one. The RSG was funny on our outing, digging into the beach sand to find stench for me, and show me how quickly it goes away once exposed to fresh air. "Here, here, smell this?" he asked, holding dripping sand-muck up for me.

Hey janet, do me a favour and keep an eye on the nitrite, i think if the sand is kept TOO anerobic nitrate will be reduced back to nitrite instead of N2........

Will do, Steve. RSG felt that nitrite would also be disposed of in this situation, which is why I was willing to go ahead and try it. I have been having problems with trace amounts of nitrite when I feed more heavily, and my poor fishies are so hungry. I will stop planting additional plants and monitor ammonia, nitrite, nitrate, and pH. Maybe I'll go do tests now....

1000ppm nitrate - that is boody high. It is said that nitrate over about 40 will harm fish in the long term. Luckily the harm, which will be on internal organs and stuff, is unlikely to manifest itself in the amount of time it takes to grow a fish to eating stage. If intending to keep fish for longer (eg breeders or ornamentals) it is much more important to keep on top of nitrate levels.

Janet, the move to incorporate an RSG filter in my system is now on, I am going to set it up in a smaller GB as a trial.

Bits that I have got:
GB container (120l/32galls)
Pipes for bell auto siphon
gravel washed in true AP style
90mm (3-1/2") pipe for the RSG filter
bag of rusty nails (rusty ones cost extra )
1kg of activated charcoal

Recipe for RSG filter:
cut 90mm pipe to length
add holes to bottom for water to exit - crenellations are an alternative
put charcoal in pipe (to what depth if using ~12" gravel depth)
mix rusty nails with charcoal
did you add coral/shell grit at this stage - what depth
fill pipe with beach sand dirty, gunky stuff?
have water from pump flowing into pipe - do not worry about overflow

I am going to hook it up to one of the sump tanks (one to right of pic) and just run it through there, this is connected to the main tank system through a siphon so the water will be doing water changes all the time it is in operation.

am I reading/following the recipe correctly

les whats RSG stand for and whats it do

"Really Smart Guy" , it is designed to gas off nitrates...Janet has done all the hard yards on the workings of one and I'm gonna come along and claim all the credit (as you do).

My nitrates are sitting on 150 and steady, want to see if a small one can work efficiently (reduce nitrates to <50) or whether I need to make a larger one, advantages are:

better for the plants - don't need that much nutrients
better for the fish - purging could be eliminated
when adding a new batch of fish - can keep them in isolation in a salty tank and not worry about nutes going too high (if the filter is effective)

your a true pioneer ekb.

i look forward to the results.

good luck.

Watts claim all the credit bit