GaryD

Greenwater Aquaculture

322 posts in this topic

Hi,

Ravnis mentioned greenwater aquaculture on another thread and thought that it was worth discussing in its own thread.

I have trialed growing fish in a greenwater culture with the algea growing to be the means of nitrification. It has worked well, but growbeds will not function with the thick solid mass that the agae forms.

I have set up a series of tubs that let the algae settle out of the water and pump it back into the tank. While I can't directly hook up grow beds to this system, I have found two good uses so far. One is that my ducks go wild for the algae and the red midge fly larvae(blood worms?) that grow in it. The other is I throw it on my small trial wicking worm bed and the growth is good. I have a watermelon plant that has vines that are ~10ft long and has produced 3 medium sized water melons. The worms either eat the algae or the bacteria growing on the algae. The only main issue I have had has been aphids, ants, and grasshoppers.

The ph of the water runs around 8 and will raise back to that in a matter of hours even when acid is added to bring it down.

You can read an article on greenwater aquaculture by a UVI researcher John Martin......here.

Vivienne Hallman, a Brisbane scientist relied on greenwater nitrification when, several years ago, she raised silver perch in tanks that had no bio-filtration. You can read about her efforts.......here. Her work is important to local micro-farmers because it confirms that greenwater culture is viable (albeit at much lower stocking densities) for some Australian species.

I think that Jim Fah's AutoPot Aquaponics system also uses algae for nitrification.

Greenwater culture is an appropriate technology idea that certainly deserves a closer look.

Gary

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The advantage of greenwater is its low cost of startup. My cost for my 6000 gallon system was less than $500, including water and fishfood, compared to $3000 dollars for for 1200 gallon aquaponic setup of which I built the grow beds and did all the plumbing. It should be able to grow 1000 lbs of fish easy if I spend a more on a high quality air pump and air stones.

While I feel the aquaponic setup is more productive when it comes to growing plants, the greenwater is ideal for someone starting out or on a budget and wanting to grow a large amount of fish with a low startup cost.

The article by John Martin was where I got the basic idea of how to get started with this project.

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Hi Ravnis,

Those are important figures for people who may be looking to do something about integrated backyard food production (Microponics) but have limited money.

Can you describe your greenwater system in greater detail? Any photos?

Gary

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I'll try to figure out how to work the camera and upload some pictures tomorrow.

The system is basically a 15 ft diameter swimming pool with air stones. I have put an exit pipe for the water to flow into a tub with a standpipe and drains into a tub below. This then goes into another tub filled with lava rocks . A powerhead with black washer hose connected to it drains back into the pool.

I also have a swimming pool pump and filter. I really dont use the filter and run it mostly on recirculate. The pool needs the extra water circulation at night and on very cloudy days, as the aglae then consumes dissolved oxygen instead of supplying it. Thus the need for a better air supply for higher stocking density. I run the big pump for a couple of hours between midnight and 2 am. I do it manually cause I am up at that time, but could do it on a timer.

I am raising tilapia, but with enough araeation and solids settling buckets, I could run this with other fish, as pointed out by Vivienne Hallman's effort of growing silver perch. The ideal fish would be one that eats algae, and can handle low dissolved oxygen levels. Tilapia is one, but I am sure there are others, I just don't know which ones yet. A fish that could gulp surface air and consumes algae would be great as long as it had a good taste.

The great thing about this is the sustainability. They will grow without feeding, albeit a lot slower. I've read about 25% of the growth rate of fed fish, but if you are looking to not have a feed cost... this will work.

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It's been too hot for me to do much weeding lately, so excuse the weeds. As can be seen from these pics. THe setup is very simple and inexpensive to both setup and operate.

The big downside is the water used for wicking beds has to be replaced. I use about 10 gallons a week in the one wicking bed.

http://flic.kr/p/8AF7Rz

http://flic.kr/p/8AF6HP

http://flic.kr/p/8AF7yH

http://flic.kr/p/8AF7kp

http://flic.kr/p/8AJaXE

http://flic.kr/p/8AF63k

Edited by Ravnis (see edit history)

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Hi,

I love the idea of using algae for nitrification.....and for the other integrations that it offers.

By harvesting the algae, you take the nutrients out of solution (in exactly the same way that vegetables remove nitrates in a conventional aquaponics system) and, in so doing, you pave the way for more integrations including using the algae for fertiliser (as Ravnis has suggested) or as food for other micro-livestock like chickens, quail....and worms.

Algae can even be pressed to remove the oil for use as a fuel.

Gary

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I also wish to try a more self-maintaining system, without too many inputs(pumps & bought food). Thanks Gary for the link to Viviennes' site. It has given me inspiration to push ahead with this idea. I have two spare tanks(1000L & 900L), which I can fill up and see how it goes. When I can get back down to Childers I'll get some more fish. I think five fish in each should do it, what do you think?

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Hi Ravnis,

Thanks for the photos......they what you're doing a whole heap easier to understand. What do you use to harvest the algae?

In reading John Martin's article (in the Aquaponics Journal), I note that they use a clarifier to capture the sludge. I'm not yet clear on whether this includes the harvesting of the algae.

I've read on another site where they use a fabric net to gather up the algae. In other places, they've used a centrifuge for harvesting.

Grassroots.....I'm unclear as to what species would be appropriate.....or how to go about it. Vivienne's experience suggested that silver perch would be OK but, outside of that, it's a matter of experimentation.

Gary

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For now, I use my two hands and literally scoop it out into a bucket and then give it to the ducks. It clumps together into a semi-solid mass.

When I first came across aquaponics, I was actually looking into making biodeisel. There was a blurb about "bioponics" and I put the biodiesel project aside. I had read about the problem of keeping an algae culture going. This might be a way to get meat and fuel at the same time. I sure haven't had any problem with growing algae this summer, but winter may be a different story.

The tubs, are my clarifier. The reason for the standpipe is to let the heavier clumps settle. I tried using it as a growbed with worms to keep it draining at first, but they could not keep up with the algae growth and it would stop up. I think it's similar to plant matter, they eat the microbial growth on the plant rather than the plant itself. The same seems to go for the algae as well.

Grassroots, A word of caution about this is that oxygen levels drop when when its not bright and sunny, so a way to provide extra air is needed. This could be a pump splashing water or an air pump.

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Hi Ravinis, I would have thought that when the sun is out there would be less oxygen(like in a algae bloom)?

Could you please explain why this is or point me in the direction of where I could find this information, Thanks

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Just the opposite. The algae produce oxygen when the sun is shining, but consume it when it is dark. This is the same for most if not all plants. They make sugars with sunlight with oxygen as a byproduct. They consume these sugars during the growth phase and use oxygen. This is why oxygen deficits occur with algal blooms, lots of oxygen during the day , and at night fish kill when they take back the oxygen out of the water. Thus the need for air stones or another form of gas exchange during dark periods. These can be just cloudy days or night time.

This is why I run the pumps from 12am to 2-3 am. I don't need the areation during the day and this much gets me through the night at my stocking density which is only 300 tilapia to 6000 gallons. I run the small 50 watt pump continously though as well as the 9L/minute air pump to 2 air stones.

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Hi Ravnis,

While I'm a long way from understanding everything I need to know about greenwater culture, it appears that it would be a much cheaper way to grow fish and provide nutrient-rich water for growing plants (probably using wicking worm beds) that a conventional flood and drain system.

Gary

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In the test cases I have read, there is a commercial farm in Arizona, a 20ft diameter tank is equivalent to a 1 acre lake. Sorry, I don't know the metric equivalents to this. But a tank 1 1/3 meters high and 7 meters in diameter would be able to raise 29000 lbs of fish according to the greenwater report. An aquaponic system would have to be considerably larger. At a stocking density that is considered high of 1 kg to 10 liters , a 131000 liter system would be required to be equivalent to double my system which would cost $1000. I will let you do the math on how much a 131000 liter aquaponic system would cost. I will say again that I feel an aquaponic system is better, but a greenwater system is ideal if costs are a major issue. It uses 1/10 th of the electricity, and startup costs are minimal, but you sacrifice plant production. While wicking worm beds work better than a dirt garden, growth does not seem to come close to a flood and drain system.

I am concerned,however, about how fish raised on algae will affect the flavor. I have no clue how this will effect it. I intend to purge some when they get big enough to harvest hopefully next month.

Edited by Ravnis (see edit history)

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Ravins,

I looked into the Algae greenwater growing of Tilapia, but decided aganst it because of the problems of PH & DO swings, not working with F&D GB's, etc.....

So i have Cultured Algae in several 5gal clear water bottles and poured out 1/2 bottle into a bucket and then poured that into a Fry barrel almost everyday, up until i went on vacation in aug, then got lax and have not feed greenwater sence.....

i add 1 cap full, Medina brand organic Hasta Grow and a cap full fish emulishion and a cap full of Maxicrop to feed the bloom, and 1-2 Teaspoon crushed orsture shell powder for Ph control in each bottle

I want to set up a Batch Culture system on boards sat on the rafters above the tanks using the 5gal bottles so that i can pump FT water & fertilizer slowly into the first bottle and then that overflows into 2 bottles, and then they over flow into another bottle each (maybe more), then slowly overflow into the Fry barrel's

I think that using greenwater feed to help offset the cost of fry and up to 4" or so babys feed is a really good idea, and need to rig up the Batch Culture system sometime soon

I also use a yeast / boiled egg yolk mixture i make up to help off set the feed cost as well.

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Hi Ravnis,

I will say again that I feel an aquaponic system is better, but a greenwater system is ideal if costs are a major issue. It uses 1/10 th of the electricity, and startup costs are minimal, but you sacrifice plant production. While wicking worm beds work better than a dirt garden, growth does not seem to come close to a flood and drain system.

I think that an aquaponics system may be easier to manage (because you can see everything better).....and it may even provide for faster plant growth.......but, if a greenwater system (combined with wicking beds) is much cheaper to build and operate, it is clearly more sustainable.

Wicking beds are like aquaponics systems (and any other plant growing system) in that they become better as they mature. I have raised bed gardens that would easily compete with most aquaponics systems for growth. I find aquaponics systems without equal for growing high value fast crops like salad greens, Asian greens and soft herbs......but most other things will grow as well in (and in some cases much better) using other growing systems.

I am concerned,however, about how fish raised on algae will affect the flavor. I have no clue how this will effect it. I intend to purge some when they get big enough to harvest hopefully next month.

I think that purging would resolve any taste issues.

Gary

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Ravins,

I looked into the Algae greenwater growing of Tilapia, but decided aganst it because of the problems of PH & DO swings, not working with F&D GB's, etc.....

So i have Cultured Algae in several 5gal clear water bottles and poured out 1/2 bottle into a bucket and then poured that into a Fry barrel almost everyday, up until i went on vacation in aug, then got lax and have not feed greenwater sence.....

i add 1 cap full, Medina brand organic Hasta Grow and a cap full fish emulishion and a cap full of Maxicrop to feed the bloom, and 1-2 Teaspoon crushed orsture shell powder for Ph control in each bottle

I want to set up a Batch Culture system on boards sat on the rafters above the tanks using the 5gal bottles so that i can pump FT water & fertilizer slowly into the first bottle and then that overflows into 2 bottles, and then they over flow into another bottle each (maybe more), then slowly overflow into the Fry barrel's

I think that using greenwater feed to help offset the cost of fry and up to 4" or so babys feed is a really good idea, and need to rig up the Batch Culture system sometime soon

I also use a yeast / boiled egg yolk mixture i make up to help off set the feed cost as well.

While I have only raised a few thousand fry now, I don't bother with fry powder and expensive feed. I just keep them with the adults and they eat the leftovers of what the adults eat. I loose some due to adults eating a few, but they produce so many it is really not a big deal to me. If I was selling the fry commercially like kellen it might be a bigger issue.

I started straining the algae from my clarifying tubs and started thinking about a comment on biomass heaters. It would be easy to be moulded into a shape and that gets me to wondering if formed into pellets and fed to a pellet stove would algae pellets burn in there. While I could press it into oil, I don't know if I would spend more energy extracting and separating it than it provided , but if simply formed into pellets and burned, might be a more feasible way to use the biomass. The ducks eat some of the algea, but quickly loose interest once the bloodworms are gone. I have never used a pellet stove before (have electric heat with really high winter bills), but this might be a quick way to make good use of this byproduct.

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Ravnis,

How long have you been raising Tilapia...? in mid Oct will be my first year of of tilapia and Catfish in AP. i got my fish from Overtons, where did you get yours...?

Based on my research, I have scooped out all baby fry, and raised them in other barrels or a bucket to keep larger sizes from eating the smaller ones, I currently have around 200 baby's from 1/2" youngest up to the oldest at about 6-7" and a whole bunch in the 4-5" range. I have lost quite a few from jumpers or other problems, but have fed most of those to the catfish, with the biggest of the cats at around 28" to 30" now, and started at 10" to 14"

do you do any Gravel Grow bed biofilters, and grow veggies, or is this strictly a fish operation in greenwater......?

what do you feed the adult's....? I was using the Cargill tilapia feed i got from Overtons, and crushing it up or wizzing it some, to feed the baby's until i ran out of that, and got a small amount of the different sizes from Aquafarms to try out.

I also feed them as much Duckweed as i can grow, the yeast /egg yolk mixture, the Greenwater from 5gal bottles, and lately, a bit of alfafa pellets and powder, and small amounts of sorgum maze for extra feed

Edited by RS_ (see edit history)

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Burning algae has to be worth a shot. You could try drying it and putting it in one of these http://www.hedon.info/TheFulgoraSawdustBurningStove

Thanks, that looks just about what I was looking for. I will have to look at it more closely. A renewable energy source like algae is claimed to be carbon neutral. The main thing is that it is wallet neutral in the long run.

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RS,

I have started several variations of systems in the last 2 years. I started with my first batch of tilapia from overton fisheries in march of 09. I had 5 batchs of fry that summer. I had a setup in my bathroom and had 1 baby survive, then had the same in a 75 gallon aquarium. I removed all fish but the mother when I next noticed her with a mouth full of babies and had an aquarium full of fry.

With the greenwater setup I found that the babies are camoflouged by the algae as as fed by the microorganisms that feed on the algae. It made rearing fry, so simple that anyone could do it.

The hardest part about greenwater is harvesting the fry, but since I just let them grow to adulthood, I just wait till they are big enough to fit in the net. It makes it hard to figure out how many fish I really have too. I see newborn fry on a weekly basis, but most become feed for older fry. This helps me limit the population automatically.

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I just moved my breeders and fingerling indoors into a 125 gallon aquarium. The fish wouldn't eat until I heated the room and then added some fillamentous algae and to my surprise they loved it and began feeding again. I was thinking of how to grow more fillamentous algae for two purposes. The first is removal of nitrogenous wastes and for food. I am intrigued by the green water concept. Am I correct is assuming that green water is caused by unicellular algae? I have watched some youtube vids of growing algae for biodiesel production. Their method is to use unicellular algae in water bottles with nutrient solution with air bubbling through.

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Unless you keep a sterile enviroment and inoculate your algae breeding tank, there could be a multitude of algae start to grow. Microscopic spores are everywhere in the air and it depends on what finds it way into your tank. One method for indoor growing would be use a separate tank and have bright light on it 16-20 hours a day. Certain strains of algae can be grown by varying the ph, but that would cause other issues too.

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Ravnis - what do you suggest for getting started with greenwater? I don't need to grow a bunch of plants or anything, like an aquaponics setup, but I'd like to grow 100 tilapia or so.

I am planning to have a 1,000 gallon tank. What sort of air pump do I need? I had planned to run the air pump at night.

As far as filtering out the algae, does that needs to be continuous, or just nightly? What sort of pump am I looking at? From some of the data I've seen, they suggest turning over the entire volume of the tank once per day.

What sort of filter has worked best with your system, just settling tanks?

Any info to help me get started would be greatly appreciated. I know there are tons of variables, but I just want to get an idea of what I need to consider.

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basic setup is 2 containers. A large one for the culture tank. A smaller container(s) for settlement tank. The idea is to pump the water slowly into the settlement tank and let it drain back into the culture tank. You will want the best quality air pump you can afford and it will be critical that it is run when the sun is not shining, but I prefer to run all the time. Get a good quality pond/aquarium pump, the best you can afford. This is the main factor in keeping your fish eating, growing, and living.

You will need to empty the solids that accumulates in the settlement tank regularly. I found by adding a flood and drain bed after the settlement tank , that I did not detect any ammonia swings. This needs to be large diameter media as some solids will still manage to clog up small gravel or hydroton. I use 1/2" diameter lava rock or larger.

A 1000 gallon tank will not support 1000 tilapia safely. One pump failure or power outage could mean a major fish kill at that ratio. I would use a minimum of 10 gallons a fish. I used a 5000 gallon swimming pool. If they are not getting enough air you will see them floating at the top and gasping for air, if that goes on too long they will die.

Here is a link that will give you more information.

http://procs.gcfi.org/pdf/gcfi_51-25.pdf

When you do decide to start, start off with a just a few fish. This lets the algae base get growing. You can quickly add more after a week. The main thing is to get the large solids out of the system, so they don't use up all the oxygen. The algae uses oxygen just like the fish do at night. They produce oxygen in sunlight.

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