Open Source Aquaponics
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2/1/15 - Aquaculture

Over the past year or so I’ve been working on fish breeding and rearing experimentation.  One of the very cool things about Blue Tilapia (Oreochromis aureus) is that they are mouth brooders.  During the breeding ritual the female lays her eggs on the bottom, then picks them up in her mouth after they are fertilized by the male.  She then keeps the eggs and fry in her mouth for the next 14 days or so before letting the fry (baby fish) swim free.  It is during this time that females will often sit in a safe place (I have PVC pipes stacked for them to hide in) and incubate her eggs until hatching.  To capture the eggs I catch all the female fish one by one and check them for eggs.  If they have eggs I simply hold the bottom lip open and move the whole fish back and forth in a pail with water in it.  I collect as many eggs as I can and then put them into a small container (yogurt cup) and inline it in my water flow.  I direct a light flow of water over the eggs to keep them oxygenated and provide small food for the newly hatching fry.  It takes a few days for the fry to absorb the yoke sack and then they look like little swimming eyeballs with tails. lol

Here’s a video of the hatching process...

As the fry grow they begin swimming and eventually find their way out of the hatching cup and into the rearing trough...

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Tilapia are doing extremely well although they have shown highly variable growth rates.  Some of them are well over 5 inches and very robust (i.e. fat) while some are still only 1.5 inches or so.  They seem to eat almost anything I throw in there including goldenberry plant leaves and strawberries.  During feeding time they really go to town on their fish food and today I noticed that some of the larger ones are beginning to display more territorial behavior which could be a sign that they are ready to begin breeding. 

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Fish are doing exceptionally well.  Zero mortality.  Their behavior varies greatly with temperature.  When temps are over 72 or so they are voracious active eaters but as the water temp drops below that, they tend to be very shy and relatively inactive… hiding in the corners or at the back of the tank near structures I provided.  Growth rates seem highly variable among the cohort.  A few of the fish are reaching lengths of around 6 inches or so, but some are still lingering behind at around 2-3 inches.  I would guess the average length is around 3 ½ inches.  Tanks are still surprisingly clean with very little solids at the bottom as one might expect.  I think the fish activity is stirring up water near the bottom as they search for food and suspending the solids long enough for them to go down the drain into the solids filter or the sump.  In addition to that I have aeration set up in each tank to move water vertically through the tanks as well as increase the gas exchange at the surface providing more oxygen to the water and allowing other gases such as CO2 to be released.  I have found no solids build-up anywhere in the system so this is a surprise (and a pleasant one I might add).  The fish are getting closer to breeding size so I've split them up and put a few into the shallow tank.  I also added a third tank heater (300 watt) which has been just enough to keep the temps where I want them.

I’m still not finding any nitrogen in the water.  Tests always come back at 0 ppm.  I think I have more than enough filtration for what I'm putting into it with regards to fish food and the infrequent feeding schedule.  I'm in the process of building an automated feeding system so they can be fed more consistently, especially now that they are getting larger.  pH and TDS (total dissolved solids) are still about the same at 8.0 and 270ppm, respectively.

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9/10/12 - Aquaculture

System has been running fairly consistently with little intervention the last few days.  Still no nitrates in the water ( 0 ppm nitrates ).  TDS (Total Dissolved Solids) has dropped slightly to 233 and pH is holding steady and 7.8.  Fish are eating extremely well and growing much faster than I expected.  I think the highly oxygenated clean water and high quality food I’m feeding them has a lot to do with that.  One of the things that’s really surprised me is how well the aeration is stirring up any sediment from tanks and suspending the solids long enough to get transported into the rest of the system where they are hyper-filtered by the sphagnum peat moss bed and sand beds. 

The fish tanks are surprisingly very clean!

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8/24/12 - Aquaculture

Fish are eating well.  Here’s a short video of the action...

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The system is running better than expected with decent flow rates through every component in the greenhouse, especially the primary Tilapia tank.  I’ve been pulling one to two little tilapias out each day as mortalities.  All very small ones that either appeared to have weak constitutions and/or got sucked up against a water outflow for too long.   I moved four of the largest tilapia into the largest tank with the larger fish as they seem to like to bully the  other small tilapia and may be contributing to some of the mortalities.  Now they’re all small fish in a big pond rather than the big fish in the small pond... literally.  They appear to be holding their own so far although the opaline gourami does give them a lot of chase.  Moved the gourami into the primary tilapia tank to see how his/her behavior changes due to population density. 
That appears to have leveled it out in terms of aggressive behavior.

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I re-plumbed most of the plumbing this week after converting the central in-ground thermal exchange barrel into a new 55 gallon sump.  My previous sump was only about 15 gallons and was very easy to flood or run dry if and water flow-rates changed within the system.  Since the conversion it has been running extremely well and relieved me of much grief trying to find a stable water management solution with a small sump.  Frequent overflows of the sump meant every day or two I’d have to add about 25-30 gallons of make-up water.  That complicated things because when you add city water to a system you have to remove the chlorine (and  possibly chloramines) that the city adds as well as warm the water up so the fish are not plunged into colder temps suddenly and stressed.


Fish arrived today!  A few didn’t make it through shipping, but most are doing well and were eating within minutes.  Sizes are a range from 1/2 inch to 2 inches.  They are quite the curious little fish checking out every nook and cranny in the tank.  I added a few round stones and some aquatic plants to help put them at ease and feel a bit more protected.  I have a feeling it will be a bit difficult to kill and eat these guys and gals in the future.

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Fish Tanks have been running for the past 6 weeks or so.  Seem to be holding up well with only an occasion leak when the water gets up near the top.  I picked up a few tin foil barbs and a couple of gourami’s from the local pet store to get the nitrogen cycle started.  The nitrogen cycle is a critical part of an aquaponics system as it is the conversion process from wastes of the fish to nutrients for the plants.  The idea of “cycling the system” is to try to quickly establish a population of microbes within the filter system to handle the waste conversion process so as to stress the fish as little as possible with the more toxic chemicals (namely ammonia and nitrite).  Typically aquariums are “cycled” by adding some very tolerant fish for the first month or two while the bacteria levels establish themselves.  Here is a chart showing what a typical concentration curve looks like during the cycling process.

The pH for the system has been around 7.5 to 7.8 which is a bit higher than I’d like for the plants so I’m researching natural methods to reduce the pH.  One idea is to create a flow-through peat component that will help lower the pH as well as release some natural growth stimulators, namely humic acid and fulvic acid.  I used peat extracts of both of these plant growth stimulators in my Master’s research thesis involving phytoremediation (using plants to remove heavy metals from soil for environmental reclamation. 

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I had to re-line one of the tanks as I messed up on the folds somehow and it would have leaked but this worked out for the best anyway as I had to drill into the sides of the tank to connect them together with PVC. 

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I got the tanks installed and lined this past weekend (April 14-15) …  They turned out nice, but whether they work well or not remains to be seen as these are experimental and most tanks of this nature that I have seen are made with EPDM rubber.  I used HDPE (High Density PolyEthylene) tarps that are food safe and fairly strong so they should work as long as I don’t jab them with sharp objects!  My cat knocked one of the quartz crystals off of the fountain and into the deepest tank puncturing it already so I’ll have to patch it.  Hopefully the patch will hold!

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