Backyard Aquaponics
A place to discuss aquaponics

synap, us "White boys" in the US may be in the same boat here soon.

Nice system lots of potential. If you try the bait idea could
it pull in more baboons? And I thought I had problems.

It true that there are starting to be more other-than-white people here. The only thing that bothers be about that is their religious and moral foundations are so opposite from those of the founding of this country. But that for a venting thread...

I love what you are doing!

Well, despite the political situation, I just put my head down and work. At least that tyrant, Mugabe, appears to have been voted out of power in Zimbabwe.

At the commercial site we have decided to incorporate an algae pond. It will be 30m x 5m and about 25mm deep. From research done locally at a university, we should be able to harvest about 1.5 ton of algae per week !!. This will yield over 2000L of bio-diesel pa and we'll use the algae for feed for the Tilapia.

Attached a photo of the university's research pond. I have graded a section next to my slab to get an idea of what it would look like visually. Also attached an image. As mentioned previously we are using 500mm PVC pipe cut in half as grow beds (image attached) Are these (250mm) going to be deep enough ??

Another concern is will my 5000L sump be big enough to pump half of my grow beds with water (flood and drain) We will have 100m of grow beds. could someone please calculate how much water these will hold. I am using 13mm gravel.

Any help would be appreciated.

Hi there, been following the thread for a while, on the baboon front, there is a local manufacture of electric fence kits that run on a 12v car coil, it will be simple enough to install a slightly modified system out in the bush, if you're interested give me a shout and I'll try get a set of diagrams through to you that would allow you to build your own. I am also interested in the wind turbines, won't you drop me a mail and give me a couple of costings. On the B / W front, we in SA are all in the same boat, all of our government are basically related to each other and positions are made available to relations rather than to qualifications. I run a large online site and have recently been offered a job in New Zealand, who knows maybe we'll have another aquaponics site that side of the world shortly (besides all the moaning - this country has so much potential and I do love it here - to start all over would be a huge sacrifice but I suppose you have to decide between sunny skies or your life at this stage of the game)

SM, that volume will be nearly 10,000L. then you need to account for the gravel.

250mm deep is fine for growbed depth

I think I should be OK. Here are my calculations.

Volume of a cylinder = pi x height x radius squared.

Each grow bed is 3m long, 500 diameter

22/7 x 3 x 0.25 x 0.25 = 589L
Cut in half = 295L

I tested my 13mm gravel and water in a small bucket. The water occupies very close to half, so each grow bed will need 148L of water.

Now I have two ponds feeding one side of the greenhouse and the other two ponds the other, each pair of ponds with it's own pump.

On one side of the greenhouse I will have 30 grow beds, set out as follows;

3 x 3m grow beds back to back with another 3 x 3m growbeds then a walkway, repeated 5 times.

30 grow beds x 148L of water to flood = 4440L of water.

My 5000L sump will thus JUST be big enough.

I am hoping to flood these GB's in 1/2 an hour.
At this stage I cannot start draining and immediately start flooding the other side because my sump will be almost empty. So say another 1/2 to drain. THEN I start flooding the other side.

It looks like I will thus flood and drain as follows;

1/2 hr flood section A (pump A on pump B off)
1/2 hr drain section A (pump A off pump B off)
1/2 hr flood section B (pump A off pump B on)
1/2 hr drain section B (pump A off pump B off)

I will have blowers running 24/7 in the fish ponds. Will the fish be happy with the pumps running 1/2 hr on and 1 hour off?

With plans for an algae pond I now have to give consideration to whether I should circulate my water (and thus the nutrients) through the algae pond and then into the sump, or merely "feed" the algae when I backwash the bio-filters.

Had to check how big your ponds/tanks were again Synapto?? Each pair (one side) 8000ltr each ? i.e combined volume of 16000ltr?

Assuming then you're flooding 5000ltr to fill the growbeds in 1/2 an hour...

That's 30% of the (paired) volume of each set of ponds/tanks.... then no further pumping for 1.5 hours....

Extracted that gives a total turnover of the water volume in each pair of tanks once very three hours....

Not sure exactly what you mean by a blower... but I'm wondering if this might be sufficient turnover in terms of oxygenation of the tanks... probably with the blower(s)....

The other question is whether the 1.5 hour "dry" period between floods of the growbeds may be too long, particualrly in high temperatures....

Maybe add another sump for the other side.... that'd mean you'd be able to flood and drain 1/2 hour on, 1/2 hour off etc... both sides

And turn your tank volume over once every hour and a half.

Just a few thoughts... comments others?

Just to expand a bit further Synapto... ignoring the "blowers" for the sake of the explanation

With the tanks (each pair) only 70% full for about a least 1/2 an hour... and then essentially "idle" for another hour... that's a considerable time that the fish biomass will be consuming oxygen from the tank and simultaneously producing fish waste.....

In high temps DO can decline pretty rapidly if you're heavily stocked and/or the fish are large and you're feeding accordingly.

Back to the previous point posted above regarding turnover.... will it be enough?

I could just turn over water between between sump and fish ponds during the drain cycle and then OFF during the B pumps flood and drain cycles. It would then be;

1/2 hour flood to grow beds A.
1/2 hour drain from grow beds A and circulate between A ponds and sump.
B is off during this hour.

1/2 hour flood to grow beds B
1/2 hour drain from grow beds B and circulate between B ponds and sump.
A is off during this hour.

The blowers blow through large airstones (attached images from my other system)

Maybe finding a way to link the blowers then pull the lines to the ponds could be better if one goes and nobody there to see it, during the night in example. Don't put them on the ground either, surprises can occur too, specially on farm type systems, i've seen floods a few times.
Maybe three blowers for two ponds, linked on a PVC pipe as reservoir and then the air lines coming out of pipe to pond.
Another thing is to increase the size of the airstone and reduce the size and speed of the bubbles, most of the air you are blowing is useless on the pic. To get airstones well tuned, they musn't move the surface to much and another thing would be putting them in the center as they would move the water column better and diffuse evenly.

You can make bio-diesal from algae? Really?

As far as linking the algae into the system you need to consider oxygen and pH. At night the algae is going to use a lot of oxygen and set the pH off. If you are using blowers then oxygen might be a problem.

That's exactly what I've been worried about, hence the idea of just using the backwash water into the algae pond. We are busy designing a press to get the oil out of the algae. After that methanol and caustic soda (lye) and voila we have diesel !!

There is a newer method to make bio diesel that does not require toxic caustic chemicals. It uses a salt catalyst and a special wick. The wick/membrane separates water from the oil and the catalyst turn it into fuel. The membrane can be washed in a washer and used over and over. The catalyst can be regenerate by heating in an oven to burn off all the waxy stuff and glycerins then used over hundreds of times.

See: http://www.survivalunlimited.com/biodiesel.htm

Their 3 micron 5 gallon bucket filter bag might even be great for a water clarifier in an AP system..

PREDATORS !!

Ok, we've had the baboons, comarants, fish eagle and now?

Lot's of prints around the dam this morning. Fish seemed very skittish, but the bird netting was undisturbed so nothing has tried to get into the water.

I have absolutely no idea what could be stalking around the dam at night. The little human-like print is about 10cm long and pointed. The other two, I suppose could be baboon, a large dog or even leopard. Very strange, but we just carry on.

The top track almost looks like a racoon track just stretched out a bit.
Do you have anything like a racoon or a coatimundi in your parts? Or a type of ape/monkey maybe.
Hope the net keeps em all away.