Aquaponics 101 – Airlift Tilapia Incubator.

In my never-ending quest to build the ultimate incubator for Tilapia eggs, I have built at least 5 prototypes, none of which worked exactly the way I planned. Summarised below are some of the problems that I have encountered in my experiments.

• The eggs were not “tumbled” sufficiently and they settled in dead spots and fungus killed them.

• The eggs were “tumbled” too vigorously breaking the egg wall.

• The eggs were washed out of the incubator before hatching and eaten by fry in the receiving tank.

• The power failed and the eggs died because they were not “tumbled” at all.

• Newly hatched fry were washed out the incubator before they were free swimming and eaten.

I discussed incubators previously here;

Mark #1

Mark #2

Enter the “Airlift Tilapia Incubator”

I have always been intrigued by airlift pumps. Using only air pressure, it is possible to pump water up without any moving parts whatsoever. You can read more about the subject here.

This got me thinking. What if I used air from my existing blowers to pump water up to and into an incubator creating a welling and oxygenation effect? So I got building. First came some experimenting.

How much air was needed to pump water?
I took an existing airline and pumped air into a 65mm PVC pipe submerged in the water.
The water rose…………………. 0 mm and all that I could see in the pipe were bubbles.
Oops, what have I done wrong?
Even increasing the air flow had zero effect. The water just didn’t rise.

After much head scratching I decided to decrease the pipe diameter.
I tried 40mm, nothing.

I then went MUCH smaller to 15mm.
VOILA, water squirted out the top of the pipe.
After a bit of fiddling, I discovered that the water rose about 50% of the depth at which the suction line was submerged in the water. This meant that If I wanted to pump the water up 500mm, I’d need a suction line submerged 1M in the tank.

Here are some images.

This is the first airlift.  The longer pipe goes down to the bottom of the tank from which water is being sucked.  If you look carefully near the bottom of the long pipe you can see the air connection nipple.  The shorter pipe goes into the bucket which acts as the incubator.

When it is mounted it looks like this.

I turned on the air and this is how it worked.

You will notice from this image the very vigorous bubbling.  I popped some eggs into the incubator to test and they were bashed around to such an extent that I just knew from experience that although this airlift was working extremely well it just wouldn’t work as an incubator.

So I put the thinking cap back on and tried to analyse what the problem was.

It then dawned on me.  The very big bubbles that were entering the suction line and sucking up the water were exploding into the bucket together with the lifted water.  This is what would do the most harm to the eggs.  In this design 100% of the air and 100% of the water was exiting the short pipe into the bucket thus causing all of the upheaval.  But how could I moderate this effect?

I figured that if I could seperate the air from the water before it entered the bucket, I could increase the water flow (by adding more air) without harming the eggs.  But how?  What if I could get the air to go one way and the water the other.  3 hours and many pipes and tubes later, I had it.  Allow the air to vent off at the highest point and the water run down into the bucket by gravity.

Here is the final result and it is working perfectly.

 

Note the volume of water existing the bucket and also note how still the water looks inside the bucket.

Update : 03/11/2009

I checked the incubator to see how it had performed over 24 hrs and I can declare this incubator my best ever!!  About 100 Tilapia had hatched and where just hanging around midway up the incubator (they would probably be washed out after another day or two when the egg sacs were absorbed and they were free swimming) and the remaining eggs all looked fine with no signs of any fungus.  Here is an image.  Note the eggs at the top of the image as I tilt the bucket towards the camera.  The lighter coloured eggs are dead/unfertilised and I try and remove them.  The others are all fine and will probably hatch in the next 24 hrs.  The hatched fry are in the foreground still with their eggs sacs attached.  These I removed to the fry tank and put the incubator back into position.

Some valuable lessons have been learned here and I have at least 4 or 5 ideas for other products from my experimenting.

Enough for now.

Synaptoman

The Clay Oven – The Proof of the Pudding

Well the oven looks good, it’s dimensions are correct, it seems to fire OK and hold it’s heat. But does it work? Well today we set out to prove (or disprove) a theory that you can make an oven out of clay from your own garden.

Step One was to start a fire. We built it up about two hours before the cooking and slowly got the clay up to a decent temperature. Then we made the pizza bases (12 in all).

Everyone then built their own pizzas using tomato, cheeses, spinach, feta cheese, salami, onions, mushrooms, bacon, ham, spicy chicken and numerous other delicious toppings.

Then they were popped into the now scorching hot oven using a hastily made pizza paddle (made out of a recycled road sign !!) This is what the first pizzas looked like in the oven.

Here is a shot of my two “assistant chefs” hard at work.

And here is what the first pizzas looked like on the plate.

After the last pizzas were cooked I popped some bread rolls in and closed the door to see how it baked.

The overall verdict was a big thumbs up. This is certainly a great way to spend a long lazy Sunday with family, good friends and a good few glasses of red wine.

Cheers

Synaptoman

The Clay Oven – Update #7

With the insulating layer completed, I proceeded to fire the oven every evening.  As the inner layer gets harder, I can build bigger fires and raise the inside temperatures.  The insulating layer fired well and the temperature caused the straw in the clay to almost char and we could smell it quiet distinctly.  Also you could see the burnt straw on the surface of the clay so it must have got very hot.  Some minor cracks developed (probably because I dried it so quickly), but these I patched and then proceeded to the final (finishing) layer.

This is a clay/sand mix the same as the inner layer but is only about 30-40mm thick and is really just to finish off the oven nicely.  You build it identically to the other layers and work your way around and around placing the mix, pushing down, pushing in and repeating.  Here is what it looked like.  Note the insulating layer showing from underneath.

As you can see the oven now reaches almost to the end of the frame.  The walls are now over 150mm thick and this should allow me to achieve some impressive inside temperatures.

I fired it once again and this time a lot of cracks developed because this final layer is thinner and also I worked in gale force winds which dried it out far too quickly.  I decided to plaster the floor of the oven with the clay/sand mix as the brick paving floor wasn’t smooth enough to get pizzas in and out.

The rustic door was completed and the door frame plastered so that the door sits snugly in the frame.  The last thing to do was to put my signature (hand print) above the door and voila, the oven was finished.  The hand print is a pagan touch and apparently man’s first signature.  Hand prints were put over traditional oven doors to protect against the “evil eye” and bless the food that was to be prepared.   Well here is the completed oven.

My next post will describe the delicious pizzas that will be made in the oven on Sunday evening and then from next week, it’ll be back to Aquaponics.

Cheers

Synaptoman

The Clay Oven – Update #6

The second layer of the clay oven is an insulating layer.  It consists of the same clay/sand mix described previously but with the addition of an insulating material.  I decided on straw.  This mixture is known as a “cob” mix and has been used in building and insulating for thousands of years.

Here is what the mix looks like with the straw sprinkled over the top.

It then gets well mixed into the clay/sand.

The cob mix is then made into bricks and built up around and around the inner layer.  I have made this layer also about 60-70mm.  As you can see from this image, the inner core has hardened to a strong smooth finish.

The layer is then slowly built up, pushing down, pushing in and then smoothing after every revolution.

This is a pretty rough layer with straw stalks sticking out all over the place.  This is not really a problem because a final finishing layer of about 30mm will seal off everything nicely.

I am busy firing the oven again tonight and the insulating layer appears to be drying and hardening exactly according to plan.  Steam is rising off of the wet clay.  The “63%” door opening is working like a charm.

I  should have the insulating layer hardened enough to complete the finishing layer before the end of the week.  Now I just need to make the door and possibly varnish and seal the timber stand and we’ll be eating bread and pizza made in the oven by the weekend.

Enough for now.

Synaptoman

The Clay Oven – Update #5

The moment of truth had arrived.  I tentatively removed the yellow board holding back the sand form and then carefully pulled out the support holding up the door frame.  Nothing moved, broke or sagged………….initially.

Then just at the top right of the door, the edge of the inner layer started to sag.  I quickly propped it up with one of the supports that I had use for the door frame and proceeded to dig out the sand.  It was like opening an egyptian tomb for the first time.

After the sand had been removed, I lit a candle to very slowly dry out the walls.  You can see the prop holding up the sag as well as pieces of wet newspaper still sticking to the walls in the next image.

I left this burning the whole day and then in the early evening started a very small fire.  As the inner core slowly heated and hardened I was able to take the prop out and spent a few hours (with a quite few glasses of wine) slowly and carefully feeding this fire, until the whole outside of the oven was warm to the touch.

Enough for now.

Synaptoman

The Clay Oven – Update #4

With a beautiful Saturday morning dawning and the Child Bride off running a half marathon in Plett with the Knysna Marathon Club, I could really get moving with the clay oven project.

Step one was to cover the sand form from yesterday with some wet newspapers (after re-checking my calculations.)

Next I measured out 1 part clay to 2 1/2 parts building sand. As mentioned previously, I have excavated the clay from my terraced garden, dried it out, crushed it into a fine powder and removed all stones. Here is the dry material before mixing. As you can see I mix on a piece of plastic. It’s then easy to pick up one side at a time and roll the mix to the center.

Then some serious mixing involving the traditional “gumboot dance”.   Add water as needed to try and get a final consistency that results in a firm (not too dry and not too wet) mix that should look something like this.

One then works from the bottom up around and around the newspaper covered sand form. Roll a handfull of clay mix, put into place push inwards, push downwards, repeat. I smoothed off the surface after every revolution. This layer (the inner layer) I have made about 60mm thick.

The completed inner layer looks like this.

I am going to leave this overnight to see how it hardens. It is not in direct sun and I’d prefer it to dry slowly, which should prevent too much cracking.  The oven is expected to crack in places and one must just fix these cracks as the occur.  Other builders have suggested only 3-4 hours before the inner sand form is removed but I think that this is because they have to cut the door aperture. My plan is slightly different and I can’t see any harm in leaving the sand form in longer. Tomorrow, depending on how it is hardened, I’ll probably take out the yellow board that holds the sand form behind the brick door arch.

Enough for now. Time for a beer.

Synaptoman

The Clay Oven – Update #3

Two steps forward, one step back.  After adding 200-300kg more weight, I decided to consult Captain Courageous, and after much discussion came to the conclusion that there was no way that the deck would hold close to 400kg.

I have now stripped all the brick paving as well as the sand underlay and with the help of Brat Deluxe (Coitus Interruptus) moved the base to another (hopefully stronger) deck.  Then I relaid the bricks, built the door frame and moulded the sand form that defines the inner volume of the oven.  As mentioned in my last post the door height must be 63% of the inner dome height.  Another important measurement is the ratio of dome height to base diameter. This should be between 60 and 75%. Here are my final figures.

Door Height = 300mm
Dome Height = 476mm

Ratio = 63%

Base Diameter = 795mm

Ratio = 60%

This should work. Here are some images of the project as it stands now.

I built a little timber deck for the top of the door frame to rest on while I cemented it in.

Here is what it looks like cemented with the inner sand form in the background.

This is what the sand form looks like.  This now gets covered with wet newspapers and the first (inner) layer of clay mix gets plastered over it (hopefully tomorrow).

Enough for now.

Synaptoman

The Clay Oven – Update #2

Good progress on the clay oven project this week. I have just finished the brick paving base. I decided not to use fire bricks as they’re a lot more expensive than normal clay bricks, so I’ve decided to take a chance and use bricks that I have lying around.

The base has worked out a lot heavier than I anticipated. I really hope that the wooden deck will hold up. That, and the insulation issues are my major concerns. Here is what the base looks like with the brick paving finished.

The design of these clay ovens is over 5000 years old and an interesting fact is that the door height MUST be exactly 63% of the overall (inside) height of the dome. Not 62%, not 64%. No, 63%. Less, and the smoke doesn’t vent properly through the door. More, and the oven doesn’t hold it’s heat. The oven that I am building doesn’t have a chimney. The smoke (what there is) vents out through the door.

The door is traditionally a rustic wooden structure. Last weekend the Child Bride and I, on one of our regular walks to Buffalo Bay, came across a beautiful driftwood beam that I have now cut up into planks to construct a door. I am going to weld (with my new-found welding skills) a metal frame. Here is mock up of the door with a piece of angle iron to show what the frame will look like.

This week, weather permitting, I hope to start the oven proper.  It needs to be constructed over a 3 day period with plenty of drying time in between the 3 layers.   I have had plenty of interest in this latest project of mine and if all goes well with my prototype, I should be building my first commercial oven for a client soon.  Watch this space.

More later.

Synaptoman

Aquaponics 101 – Comparing Apples with Apples.

I often use a saying on the various forums that I frequent on the Internet, “When your only tool is a hammer, everything looks like a nail.“

This is so true for many of us, and one of my pet hates, is a person who is so set in his ways that he is blind to better and more efficient ways of doing things.

I am one of Aquaponics biggest fans, and use this blog and numerous other forums to sing it’s praises. Does this mean that Aquaponics (AP) is better than traditional soil-based gardening? Does it mean that the fish produced in AP systems are better than the same fish produced in a proper Aquaculture system? No, of course not, but what I do believe, is that AP has many applications in situations of poor soil, limited space and scarce resources (like water).

When it comes to vegetable crops, not all grow well in AP systems. Some don’t grow at all (like potatoes) and others grow slightly (or much) better in soil. I need to have this sort of practical experience on hand in order to advise clients. This is one of the reasons that I recently established an earth garden to trial various crops against those grown in an AP system.

Let me start by admitting that I do cheat somewhat. How, you may ask? Well the plants in my soil garden have the benefit of being watered with “fishy” water from my AP system, so they do have the benefits of both the nutrients in the soil and the Nitrates from the fish.

The results of my trials, although still only early in Spring, are quiet interesting. Here is an image of spinach grown in gravel in my AP system.

And here is the same spinach grown in ordinary soil, but irrigated with “fishy” water.

Not much difference, other than the fact that the soil-grown spinach looks darker.

Here are some early images of various crops grown in soil, much of which is reclaimed lawn. As far as I’m concerned a lawn is just a waste of water and the great thing about veggies is that they don’t need to be mowed.

Swiss Chard (spinach).

Butter Lettuce.

Lettuce, tomato seedlings, swiss chard, squash, watermelon.

This weekend we harvested about 3kg of fresh garden peas and they are delicious. Here they are in the bucket and what the peas look like in the pod. Yummy.

Makes me quiet hungry.

Synaptoman

The Clay Oven – Update #1

As mentioned in my last post, I have embarked on a project to make a traditional clay oven. The design is thousands of years old and ruins of clay ovens have been found on all of the continents. Because I hate doing things normally, I decided that my clay oven would be built on a timber base and stand proudly on my deck, where the whole family could help with the bread baking, pizza making etc.

I have now finished the frame, which I suppose I have over-designed (again). It offers a sturdy base with the weight evenly distributed across the bottom.

My main concern is to keep the heat contained and the underlying timber very well insulated from heat of any kind. The base is made with a timber decking floor insulated with a sealer which can apparently withstand 1200 deg C. We will be testing this !!

It is then covered with a 2-3cm sand layer (about 1 inch) adding further insulation.

As you can see on the right of the image, the bricks will stand slightly higher than the frame. Because of the cost, I am using genuine fire bricks under the oven itself but ordinary bricks for the surrounds. I am hoping to get the bricks this week.

Enough for now, I think I’ll order a pizza !!

Synaptoman