Aquaponic Gardening

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I am Amy from Los Angeles. After almost three months, I finally finished my system and it has been cycled for a week. Thank you everyone who helped me in this fun project. Currently, I have four medium size tilapia in the fish tank. It's already have some fish poo settled at the bottom of the tank. What I need to do to get them out into the grow beds? The only thing I can think is adding a lot of air stones with an air pump to get all solid waste suspended in the water.

My system is a CHOP system with two IBC totes. One tote was cut into a fish tank and a grow bed and the other was cut into two sump tank. Water from fish tank flows into grow beds by gravity through the original valve of the tote. Water of the grow beds drains into sump tanks through siphons. Two sump tanks are connected and the water was pumped back into fish tank by Quiet one 4000 pump (about 900 GPh). To avoid using an air pump, I have add a Venturi system in the pipes from sump tank to fish tank. It definitely add more air in the water, but it's not enough to creat enough agitation to suspend the solid waste. To prevent the overflow of the fish tank, two sets of overflow pipes come from fish tank to sump tank.

Any suggestions of how you deal with the solid waste will be helpful. Any critics or warnings of my system will be more than welcome.

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It's not the $20 radial filter that I'm looking at as a significant expense, but rather the ongoing expense of fish food  Like Harold alluded to earlier...it comes down to operator choice. Those choices will be shaped by many things, like the wishes/desires of what the operator wants out of his/her system, costs, location, experience etc...

For instance, I'm probably paying about double what you are for quality fish food here in my area. This in part, drives my desire to try and get the most out of every mg of that feed (in terms of plant growth). So does the fact that fish feed is manufactured in a horribly unsustainable way, and is one of the vectors through which our Oceans are being indiscriminately emptied. This does not really jive with my sensibilities and adds yet another, non-financially driven, reason to want to get the most out of every crumb and molecule of feed.

You may say, 'hey, don't you have plenty of fruit trees around and a big dirt garden which might benefit from the excess sludge'? Sure, and that's perfectly valid and all, but I'd like to get the AP to a point where it's a streamlined standalone functioning model in my area (it may always be a part of an integrated-farm-whole, but I've not let that keep me from trying :) Anyways, folks should probably do what it is that works for them and what they're happy with...both of which may change over time...

@Vlad - I totally agree.  As you know I favor bioponics over AP.  But I now find myself caring for 60 tilapia and 20 catfish neither of which I enjoy eating. You once described AP as a romantic attraction, that is exactly what keeps me involved. 

I see AP as wasteful of energy, and as you pointed out fish food is an expensive fertilizer.  That cost is only somewhat justified by the production of fish.   If it were not for fossil fuels many of our farming habits would not be possible.  There are very few methods to raise animal protein that do not rely on growing grain.  Free roaming pigeons comes to mind, but even then, they are probably eating someone else's agricultural produce.

For many the premise of AP is about conservation.  Some even aspire to bring AP to countries where water and good soil are scarce, or provide food in case of total economic collapse.  That is absurdly blind.  Even without accounting for the energy costs of fish food; AP has a negative energy sum when the energy required to pump water is accounted for, and using solar energy does not justify the negative return.  Besides that, AP growers will find themselves relying on fish food from sources that may no longer be available. Hardly any better than synthetic fertilizers for hydroponics.

If the goal is conservation and independence; I suggest learning to live and farm with permaculture, which will also help sequester carbon in the process. Even land that has been made into barren wasteland can be revitalized, and turned into productive food forests with permaculture.

So back to radial filters.  Some AP growers have found it necessary to reduce sludge accumulation.  If fish production is justifying the use of fish food for fertilizer, then we had best optimize the entire system including the water quality for the fish and roots by removing the excess, and spreading it on our permaculture garden. 

Permaculture utilizes aquaculture as nature would.   Ponds provide micro climates, water reservoirs and are home to fish, birds and a variety of other creatures, and sludge takes care of itself.   Just yesterday I saw a quail run out from my tomatoes with a green worm - it's synergy.   The goal should be to improve and create more than we take.  Recycle nutrients, or obtain them from sources where they would otherwise be wasted (don't piss it away, use bioponics), conserve and gather water in ways that require no fossil fuel.  Let nature share, and help in the garden. AP provides a romantic attraction, and it's fun so do it for that, but conservation is probably not one of it's best attributes.  It might be suited to space travel, but we are here on Earth right now.

1) is it just me, or is 900 gallons per hour a bit much for four tilapia in a 275 gallon tote? I have 264 Gph pushing water in my system (same size as Amy's) for 17 bullheads and a few minnows, and they don't seem to be deprived of oxygen.

2) I have found with catfish, they spend all day huddled in the darkest corner of the tote, wrestling for position at the bottom of a dogpile (fishpile?). The result is a lot of circulation throughout the tank and especially across the bottom, with the effect of sweeping solid waste toward the SLO pickup. In regard to other comments that have been made, I'm not sure if you can get a squarish tank to circulate in a way that is circular enough to get poop to collect in the center. If not, having the "catfish sweepers" might be a viable option for you.

3) it looks like your fish tank is elevated to a level that is much higher than everything else, with the effect that there's high pressure in the line that feed the grow beds, and you're using (ball) valves to restrict the flow into each bed. I don't know if you are finding it a problem that your fish tank is so high, but personally I find it convenient to have the IBC on the ground so I can look at my fish with both feet on the ground. Maybe safer, too, given that we live in earthquake country. As long as the fish tank water level is higher than the outflows to the growbeds you should be able to get gravity to do its work.

@Jeffery -  I too like my fish tank lower.  My fish tank, gravel bed, and DWC beds are all at the same level.  This allows maximum circulation with very little head loss and like you said, a good view of the fish too.

Thank you so much for all the comments and discussion. I learned some much here! The fish tank is about 250 gallon and I have 6 of cement mixing tray (24in x 36in x 8in) and one upper part of the tote (42in x 48in x 12in) as grow beds. According to 7.5 gallons per cubic foot of volume, currently, I have 1:1 ratio of grow bed to fish tank volume, which is at the lower side. So I will probably start with 20-30 fingerlings after my system has finished cycling. I am learning everyday from the operation of the AP and from the forum. I was stupid to introduce five medium size fishes to the AP in the middle of “fishless cycling”. One of smallest fish was sucked into my drain pipe the next day J and I know I need to add a screen. Currently, I am experiencing a nitrite spike (5 ppm or higher) which cannot be determined by the API test kit and the nitrate level is about 40 ppm. Three slightly bigger fish are fine so far, but a smaller one is suffering so I have to isolate it into a separate bucket. Any suggestions of how to accelerate the growth of Nitrospira which converts nitrite to nitrate? According to Sylvia’s book, the optimum pH range for Nitrospira is between 7.3-7.5 and the pH of my system is about 8.0. Will that help if I adjust pH down a little bit? Will adding Maxicorp help?

With three medium size fishes in the tank, I already see some solid waste and that reminds me the warning from Jon Parr “solids settling and making nasty anaerobic slime sludge in the bottom of the fish tank”.  I am trying to design something to prevent that happens. I have thought about grow some catfishes, but I have read somewhere in the forum that you need to add salt occasionally into the system to keep the catfish not getting sick. Bob and Jeffery, have you had any problem of growing them together? If not, how many catfish will accompany well with 20-30 tilapias?

Since my system hasn’t start t run at its full capacity, I am not sure whether I will experience the sludge problem in the grow beds. How can you tell there is a problem? Will siphon get clogged and not working or you get bad smell in the grow beds? I will definitely introduce some worms in the grow beds soon.

Jeffery, you are right that my fish tank is too high and it’s not necessary. Unfortunately, it’s not possible to fix that problem with water inside. I will lower it by removing some brick blocks when I get a chance. Will high pressure in the line and ball valves restricting the flow cause a problem? Actually I have encountered some problems on the flow rate. The flow rate of four grow beds close to the fish tank always get slower, but that of the other three grow beds at far end stay the same. Is this issue related to the high pressure in the line?

Hi, Amy.

I think you'll just have to wait it out to get past the nitrite spike. You're fine at pH 8.0--for the bacteria anyways. Your plants would probably prefer under 7, but that's going to be a tall order with our water source in SoCal.

I have only bullhead catfish (no tilapia) in my IBC, so I can't comment on how well they get along. I can say that I don't salt the water and so far they're okay.

Could it be that the valves closest to the fish tank are the ones getting occluded by fish poo faster, and that's why they get slower moreso than the ones that are more distant? If you open the valve wide when it gets slow and chunks come out, there's your answer.

The pressure per se isn't really a problem...unless a valve pops out or something and the fish tank just drains out entirely--that would not be good.

About the screen on the outflow from the fish tank--it can get blocked by larger fish turds, algae, dead fish. If this happens you'll lose flow to the grow beds. Large mesh helps, and it's a good idea to have some easy way to jiggle the screen to dislodge softer bits that get stuck on the mesh and slow flow. 

Amy - Here is an example of sludge. Some people find that this sludge clogs the media too.

I have not found the additives to speed up the colonization, but if you can bring some media from an existing system to yours it might help.

I believe Carey Ma keeps catfish and tilapia together.  I tried it and the catfish looked frightened so I moved them back into their own space.

Don't be too quick to add worms.  You need something for them to eat and if your system is new you may find yourself rearranging things.  

Amy,  I have a setup very similar to yours and I have tilted my fish tank slightly downward toward the outflow side of the IBC. This makes it so I have slightly less water in my fish tank, but it also makes the solids that settle in the bottom migrate toward the outflow end, where they are sucked up in the SLO.  I seldom see solids accumulate in my fish tank and I have 40 tilapia that are becoming quite large.

Vlad, How do you deal with the accumulation of solids in your grow beds as the fish become larger and the systems capacity is tested?

Bob, what do you do with the solids you remove? You allude that you use them in your soil gardens, but do you first compost them?  How do you apply it?

Hi Amy,

Please don't feed the fish in your system until it becomes fully cycled.

Hi Roger,

Part of my whole "deal" is trying to implement operational methodologies that will test the bounds of the ultra-low-density end of the spectrum, and yet still have plants do well. So my system is very far from approaching it's bio-mass (fish) capacity. The GH system holds about 18,000-20,000 litres (about 4,800 of which is fish tank). The 8 IBC's that I use for pre-filtering all get an equal share of solids (made possible by a sequencing valve)...so no one bed gets the brunt of the sludge (which helps). Another thing that helps is that I barely have more than twice the mass of fish that you do, (there are a number of things which allow me to operate this way) so I don't really have a problem with solids building up to deal with. My GH system is very much a plant based one...

Recently I've been 'playing' with specific strains  and combinations of specifically targeted strains of bacteria for the purpose of solubilizing both organic and inorganic phosphate compounds. I have a PhD microbiologist lady friend who has made this possible. This phosphate solubilization at least appears to have the positive side benefit of reducing some of the solids, but this effect seems to be pretty slight and secondary to my purposes. (There are more phosphates in fish effluent than anything else, so by mineralizing the phosphates the sludge is reduced). But I'd use very different bacteria if the point was just getting rid of sludge. 

If I had a system where the main game was lots of fish (which would mean lots of excess sludge), in addition to composting worms, I'd probably employ the services of various detritivores (gammarus is a popular and easily procured one)...then, what the gammarus didn't take care of I'd use a combination of even smaller organic sludge loving organisms like Lactobacillus casei and Rhodopseudomonas palustris...These little guys are often used in disaster clean up operations, like Hurricane Katrina or the S.E Asia Tsunami's...and massive flooding scenarios and the like...as well as in waste treatment facilities for the very purpose of "composting" and reducing sludge mass...

I wanted to work a bit more seriously on a self-contained, bacterially based unit for AP that 'gets rid of' solids without removing their plant essential element content from the system, but since I personally don't have a problem with solids, I've not been real motivated on that front. I have however (like most everybody, whether they realize it or not) run into phosphate bio-availability issues (particularly pronounced with such a low density system)...so that was the problem that I chose to work on this season :)

Roger Baldwin said:

Amy,  I have a setup very similar to yours and I have tilted my fish tank slightly downward toward the outflow side of the IBC. This makes it so I have slightly less water in my fish tank, but it also makes the solids that settle in the bottom migrate toward the outflow end, where they are sucked up in the SLO.  I seldom see solids accumulate in my fish tank and I have 40 tilapia that are becoming quite large.

Vlad, How do you deal with the accumulation of solids in your grow beds as the fish become larger and the systems capacity is tested?

Bob, what do you do with the solids you remove? You allude that you use them in your soil gardens, but do you first compost them?  How do you apply it?

I dump my sludge on plants around my yard.

Roger Baldwin said:


Bob, what do you do with the solids you remove? You allude that you use them in your soil gardens, but do you first compost them?  How do you apply it?

How long fish can survive without feeding?

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