Building the Aquaponic System - Part 3 of 3

This is the last of the series on how my aquaponics system is put together.  It details how the media and raft-based beds are designed and assembled.

This video shows how the various grow beds are set up in the dome greenhouse.  In order to maximize as much floor space as possible, all the beds are custom fabricated.

There are three media-based beds located in the center that are filled with expanded shale.  The beds use bell siphons to flood-and-drain the water which drains directly back into the central sump tank.

Along the perimeter wall, there are 2 media beds.  These beds are set higher than their neighboring raft-based beds and drain directly into them.  This method works very well since the media beds filter all the solids from the system and minimizes the amount of sediments that could accumulate in these raft beds.

I’m undecided on the last two beds and may make them rafts beds and interconnect them with water bridges, or have one (or both) be media-based beds.  It all depends on the types of crops I eventually decide to grow.

I drew a chalk outline on the floor that acted as a template for all the beds.  The frames are made from 1/2 inch black pipe that I welded together.  I’m using steel since it is very strong and doesn’t warp like wood, and is resistant to bugs and rotting.

The sides of the beds are 12 inches high, which seem to be a good depth for both raft and media growing.  Leaving for a little extra space along to top so the water and media doesn’t spill out, the growing depth is around 11 inches.

The bottoms have support braces spaced every 12 inches.  My original plan was to have the raft beds sit directly on the brick floor, but I had one critical design flaw in the dome… I ran the ducts for the geothermal out through the floor and the beds would block them.  I had to prop all the beds up on a brick so the air could pass under them.

When the steel cools off after welding, a little black rustproofing paint is applied which cleans up the look a bit.

This is one of the raft beds that was going to placed directly on the floor but interfered with the heating system.  Instead, a few bricks are placed under it as feet and the frame is set into place.

Back in the spring, my neighbor and I milled a bunch of the white pines that I had cut down from the greenhouse site.  Some of them are cut to 1 inch thick and are being used to line the grow bed frames.  I just laid them into place and let them overhang over the edge, marked a cutting line, and cut off the excess.  They lie down nicely and make a very strong decking for holding the liner.

The media bed is assembled the same way but is set on stacks of extra bricks.  The bottom elevation is higher than the top of the raft bed so that it can drain into it.

I purchased a large roll of EDPM pond liner.  It’s very heavy and difficult to work with, but is hard to puncture and is UV resistant.

The liner covers the entire bed and I carefully make sure it is properly centered so all the edges can be draped over the lip of the bed.  I did discover that it’s a lot easier to work with the EDPM if it warms up in the sun…even though it’s hot on the hands.  I just keep working it into each corner making sure that there is plenty of material to fit into the corners.  If there is a gap between the wood and the liner, it could stretch and eventually tear under the weight of the media and water.  I found it was very helpful to set bricks on the liner once I had it in position to hold it in place.

The corners can be a bit tricky.  Once I got the liner in place, I cut off some of the excess to make it easier to manipulate.  Then I could fold a nice and clean corner. It’s important to remember to make sure the edge of the liner is always going to be over the lip so water won’t leak out!

On the outer edge of the bed, I added a strip to anchor the liner into place.  The screws go through the strip and liner, and secure into the side boards.  The extra liner is cut off which makes for a clean looking transition from the liner to the bed.

The media beds have bell siphons in them.  I’m using a bulkhead fitting through the bottom of the bed for the drain.  So that the liner doesn’t get tangled up in the hole saw, I sandwich the liner under a piece of scrap board.  These boards a still somewhat damp and the saw is old and worn out so I have to keep cleaning the sawdust from the bit, but eventually I make my way through.

After cleaning the debis out of the area, the bulkhead fitting fits perfectly through the hole. It has a rubber washer that seals against the EDPM liner and fitting.  Under the bed, it has a large nut that tightens the fitting in to place.

The stand pipe and drain lines are made from 3/4 inch thin-wall pipe.  These bulkhead fittings have a 1-1/8” threaded fitting since it’s what I had in my assorted collection so they need a threaded to slip-fit coupling to reduce it to the right size.  I use a temporary stand pipe and fill the grow bed to test it for leaks.  I like to fill the beds right up to the rim to test for a worse-case scenario.  Plus it’s a great way to check to see if the bed is level and add any shims to the legs for minor adjustments.

Once everything looks good I put in the bell siphon and media guard, and the bed is ready for the expanded shale.  Since I recorded this video, I’ve changed the bell siphon design a bit, so click on the link to see these details.

This type of bell siphon uses a trap which helps it to start.  The trap assembly is screwed into the bottom of the bulkhead fitting and a section of pipe is attached to the trap and extends to drain into the raft bed.

The liner for the raft bed is installed the same way as the media bed.  It was actually was a bit easier setting it up in a larger area.  Once the liner was installed, I flooded the bed and removed the temporary holding bricks.

I’m using expanded shale for the growing media.  I just give it a quick bath to rinse off the dust, screen out some of the smaller stones, and fill in each bed, one bucket at a time.  I like using the shale since it’s about half the weight of stone and easy on the hands while digging in it.  Most of the corners are rounded over which will minimize the risk of it puncturing the liner.

Since the raft beds aren’t square, I needed to come up with an efficient design to maximize the space of the bed.  Using square rafts would never fit properly.  I design a single row raft that was tapered so they would “fan out” in a curved pattern when they were placed in the bed.  As the taper became wider, I placed the holes closer together.  For a mature plant, the amount of space per plant will be the same, it just is not a perfectly round or square area.

The seedlings will start from one side.  Every few weeks, a new batch will be added and the older seedlings will get moved over.  At first, the width of each raft is narrower than the space that the plant will need, but as it grows, I add a spacer in between the mature plants to give them a little more room.  By doing this, I can compact the new plants together without having to transplant them from a compacted raft into a normal-spaced raft.  Each bed will hold about 208 lettuce in about 44 square feet.

The remaining area can be used for seedling starting.  Currently the space works well for growing duckweed.

The rafts are made from 1” Dow blue board foam.  I made up a template so each raft was cut identical.  The template also has holes that marked the location for each hole for the net cup.  I used a 1-7/8 hole saw which makes for a snug fit for the 2” cups.  I found it was fastest to drill the hole half-way through, then finish drilling from the other side.  This left a bit of the plug sticking out so it was easier to remove from the hole saw.

I fill the net pots with a little bit of damp shale and drop in one or two seeds.  The dampness makes the seeds stick to the shale so they don’t just drop through.  The rafts push right over so the new set can be placed at the beginning of the bed.  Once the plants mature and need more space, the filler rafts can be inserted between each row.  So far, the lettuce has a good healthy root system and will be ready to harvest in a couple of weeks.

Thanks for watching this series, don’t forget to like this video and join us on our Facebook page.

Automatic Fish Feeder

Time to add to my laziness and add some more automation.  I no longer have to feed the fish a few times a day...however I still like to just stand there an watch them.  What is it about them that's so mesmerizing???




This is a small automatic feeder that I made which holds about 4 tenths of a liter of fish food and has been running for a few years.  I built this larger one for the new greenhouse which holds 2.8 liters.

The feed is controlled by a regular 3/4 inch wood auger bit which fits nicely into a housing which is a piece of 3/4 inch black pipe.  This is driven by a 12 volt DC gear motor I got from a surplus store.  This is a great motor since it has a slot instead of a drive axle so it’s easy to make the auger bit fit into it.

First I cut down the auger bit to the right length and grind down the shaft so that it fits into the slot of the gear motor.  I then cut out the center of the black pipe.  This is where the feed hopper will connect to the auger housing.  A small piece of flat bar is used as a mounting bracket which will allow it to be mounted to the tank and attach the motor to the shaft.

After carefully setting up the pieces, I tack weld the auger housing to the mounting bracket, then remove the motor and finish welding the pieces together.

The feed hopper is made from an old computer cover.  I made up a cutting template for the various pieces and sprayed adhesive to the cover to hold the templates while cutting.

I built in some tabs to the hopper walls so I could weld the pieces together.  This is the point in time where I which I owned a metal break, but had to improvise with my vice and hammer.  Luckily, the bends were not too complex.

After all the pieces were bent into shape, I ground off the paint so the seams could be welded together.  I also drilled holes through the walls where the tabs would connect.  This is so I could weld a tack through the hole to connect the thin sheets together.  It’s similar to riveting the pieces together.  

When the hopper is welded together, I grind the welding tacks down so they are flush with the sheet metal.  The last bit of welding is to attach the auger assembly to the hopper.

I am fortunate to have access to a nice sand-blasting cabinet.  This quickly and easily removes any loose paint and rust and makes a really clean surface to paint.  After a couple of coats of paint, it looks almost as nice as work done by a pro ….almost.

I made up a level switch that turns on an LED to let me know when the feed is getting low in the hopper.  I took a bamboo skewer and hot-glued it to a micro switch.  The newly extended lever reaches into the hopper and has a float that hangs from it.  When the level goes to low, the float will pull down on the lever and light the LED.  I also added a momentary switch into the box which allows me to turn on the auger in case I feel like giving the fish a bonus snack.

I mounted the level switch box to the hopper and connected the motor wires through the box.  Then the new feeder was bolted to the side of the stock tank.  For now, I connected the feeder to one of our IX-180 index timers.  It is programmed to run the auger bit for 20 seconds, four times per day.  The extra input of the timer is used to monitor the water temperature in the tank.  Eventually, the feeder, vents and other controls will be connected to a master automation system.

Here’s the float that sits on top of the food, when it gets low enough, it just pulls down on the lever and turns on the LED and this is the feeder in operation.     Thanks for watching!  Make sure you subscribe to this channel for more great videos!

Plastic Extruder for Growing Media

For several months, I’ve been developing a plastic extrusion system that has been able to take virgin HDPE resin pellets, or shredded milk jugs, and properly melt and extrude them into a shape that could be used as a low cost growing media for my Aquaponics system.

There was a lot of trial and error to get to this point. The biggest problem is that the plastic retains little moisture. If the seeds aren’t directly placed in the flood/drain cycle, they won’t get any moisture to germinate. I typically grow in stone and some of the stone above the water line is able to wick and retain enough moisture to provide water to new seeds.

Another issue with HDPE is that it’s extremely smooth (again, works well to repel water). Even adding texture to the media during the cooling process, the media still is smooth, which makes it difficult for bacteria to stick to it. I was also a bit surprised to see that the roots didn’t really care to grow in it and they would grow around the edge of the net pot instead.

On the plus side, the plastic is light, fairly inexpensive, clean, and easy to work with.

I hope some of the info in the video is useful to some of my fellow aquaponic/hydroponic growers in their quest to find a better, more cost effective growing media.

EDIT:  There is now a second blog entry with some more details about this.... Click on the "Newer Posts" link near the bottom.

Below is the transcript for the video…no need to read it if you’re going to watch the video… I just included it so some of the search engines could pick up on the keywords. ;-)



Hello Everyone. Today I’m going to show a plastic extruder system that I built. The end result was to produce a synthetic, cost effect growing medium for my Aquaponics system.

The extruder consists of a hopper for high density polyethylene pellets. An auger then forces the pellets through a dual zone heating chamber. The heated material is forced through a small die at the end of the chamber.

The temperature in each zone of the heating chamber is controlled by a Teensy AVR microcontroller which is monitored and adjusted through its USB port connected to a laptop.

The auger is driven by a windshield wiper motor and it is geared-down using an old bicycle sprocket and chain.

The hopper is filled with HDPE pellets where they are slowly forced into the heating chamber. It can also be filled with shredded milk bottles or shredded milk bottle caps to add color.

The heating chamber is covered in some fiberglass insulation to conserve heat. There are two thermal probes mounted near the middle and end which provides accurate readings to the controller as the material is heated. The heating elements draw around 16 amps at 12 volts.

The molten plastic that is extruded from the die is squeezed through a set of rollers which embed a texture into the material. A small tube blows air onto the pressed material to cool it, and to keep the rollers cool.

This is one of the rollers after I turned it on my lathe with a close-up view of the texturing.

And this is a close-up video of the material being extruded and pressed through the rollers.

Here is a close-up view of the finished material once it has been cut to length. There is a waffle pattern embedded into the plastic which provides plenty of surface area for bacterial growth. The media lies flat which helps to retain moisture during a drain cycle. The pieces have plenty of spaces between each other for water and root growth.

Most HDPE plastic is classified as food-grade. However, one problem is that nothing likes to stick to it. Even though a texture has been embossed into the plastic, a small amount of movement can disrupt anything that was clinging on it.

This is a time-lapsed video taken with my PlantCam over a 30 day period. There are 3 bean plants growing. I also planted lettuce seed which didn’t germinate, probably because the top inch of the media doesn’t retain moisture like stone or expanded clay.

After 30 days, I removed the beans from the aquaponic system. I had the net basket wrapped in foil to prevent the roots from wandering into the surrounding stone. The roots seem to have an aversion to growing in the plastic and mainly grew between the basket and foil.

Thanks for watching. If you have any questions or comments, please leave them in the comments section below. Also please subscribe to my YouTube channel to see future videos!

Indoors Aquaponic System

This is my new indoor system. I built it to replace the charcoal filter for my 45 gallon fish tank. I was spending about $5/week on these filters and would take about an hour to replace the filters and change out the water. This new system has been running for around 3 months and I haven't had to change the water. As an added bonus, we get some tasty lettuce!

I'll admit it...I love automation. So it takes a day to build something where it normally would take 10 seconds to manually feed the fish....it's well worth it! My latest creation is a fish feeder.

I took a small gear motor and slightly modified an old auger bit that was laying around. Then welded a couple of pieces of black pipe together and stuck a cam and switch on the end. A 7-up or mountain dew bottle makes a great feed holder. I probably could have made it independent and put it on it's own timer, but I have it running off of my computerized controller that runs the rest of the system. The only think I paid for was the gear motor, which was around $12....plus I lost my $0.05 deposit for ripping the label off the bottle. It works great! NOTHING gets stuck in there and it could easily take off a finger if you stuck in in the feed tube. After all, the bit is made of hardened steel and is designed to drill through wood!






Here it is all up and running. Right now my goldies are small and are still on flakes...and there's some pellets mixed in there.