What's This Have to Do With Making and Biology?
This planter is a test article for a much larger aquaponics system. Besides allowing users to grow their own plants and fish, and other aquatic organisms in a finely tuned environment, it also provides organic food, potential input materials for projects, and a biological microcosm for observation and experimentation -- all of this on either your balcony, near a window, or on your rooftop.
It can also serve as a test bed for various forms of automation. Although this test article may be destined to hold a single plant, what is learned from making this minute planter will be used in constructing the full sized prototype. To see projected progression of the project, please see our earlier post here. This is the "concrete planters" stage.
What Was Learned?
Starting small is a good idea because you are likely to make a lot of mistakes. For one, I didn't mix enough concrete so it came up short as you can see -- it didn't even cover all my letters for "HELIOS" with most of the S missing.
Two, at the last minute I realized I had no provisions of putting the concrete into the form from my large ungainly bucket -- so I took out the inner form and poured all the concrete in thinking I could push the inner form back in. That didn't really work either and luckily my form was strong enough with plenty of tape to handle the moving around.Finally, and they warn you about this but it is still a very easy mistake to make, I accidentally put in too much water while mixing the concrete, meaning I had to add in more cement until it became the right consistency. ALWAYS start with just a little water, mix it in completely before adding more.
I let it sit in the mold overnight and for half the next day before opening it up. The letters "HELIOS" I put in seem very "incorporated" into the concrete now. I'm not sure they will pop out and leave the imprinted look I was going for. This small planter is very heavy -- something to plan for when making the larger actual prototype aquaponic system. This was only about 6 liters of concrete, the full-sized system will use at least 30 liters. A dolly with wheels or wooden skids might be a good idea.
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| On the right you can see the cardboard form used for the test article. Next to it on the left is the full-sized prototype. After working with the smaller cardboard form and observing several limitations with it, it may be a good idea to look into alternative forms for the larger version which will hold 10-15 gallons (38-56 liters) of water. |
Also, if you care about this, the cardboard form, where the tape was carefully applied, is incredibly smooth with an almost polished appearance. However, most of the tape on my form was not carefully applied and as you can see in the picture, it looks rough. I like it but if you don't, make sure your form is smooth because whatever imperfections it has will translate directly onto the concrete.
For the concrete mix, I used 1:2:3 cement to sand to small fish tank-style gravel and about one more part water. The rest of the steps followed along with this tutorial found on Instructables.
It's going to be a little more planning for the full-sized prototype. This test article still needs to be examined in terms of strength and its ability to hold water. I may look into alternatives for forms instead of concrete for the larger article to avoid a disaster. A 30 liter concrete pour into cardboard forms may be pushing the limits of concrete-cardboard technology.
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