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Micro-Hydro Project
 
 

What is it?

This is a design for a micro hydroponic bed that can be made at home from junk, and be used to grow herbs and vegetables (and flowers, of course).

 

Hydroponics (from the Greek) literally means ‘working water’.  θαμνώδηs γένια is the Greek for ‘Bushy Beard’ according to a dodgy online translator, but I digress…

 

Hydroponics is a broad spectrum of techniques for growing plants without soil, by carrying nutrients in water.  Some techniques suspend the plants in water (on a float or in a clamp), some spray the roots, other use various media to support the plant. 

 

The technique we will discuss uses Quincan, or volcanic scoria, as a medium, and a commercial two-part nutrient mix added to re-circulating water.

Why do it?

Perhaps you have a concrete garden, or a small balcony – possibly in an atrium.  If you are away a lot, pot-plants can dry up.  A hydroponic system generates around ten times the produce of a similarly-sized land plot. A hydroponic system is very water-efficient, especially if the plants are mature and form their own microclimate.  Foliage will efficiently shield the growing media from the sun and cut down on evaporation.  You could always get technical and install a water line and float valve.  Mainly, do it because you can grow goodies efficiently in a confined space.

Don’t I need grow-lights and fans?

This system is for use outdoors in the sun.  Roll it under cover when it rains or if it gets too hot out there.  You should design any power feed to be water-resistant, so no exposed plugs or sockets, and an RCD trip extension lead is only sensible.  A little rain is fine and will replace evaporation; major downpours will dilute the nutrient.

Why recommend it?

Some people find it difficult to understand why we would recommend people to grow their own produce and herbs when we make a living from doing it.  The answer is that we are trying to make the pie bigger, rather than get a bigger slice.  Nothing makes you appreciate the effort the professionals put in more than trying to grow a range of herbs 365 days a year.  Anyone can grow a pot-plant on the window sill in the growing season – the trick is to be able to supply good quality produce all year round.  We also believe that few people will go back to processed herbs when they have fresh herbs available.  Of course there is a need for dried herbs – but some are a waste of space, in our humble opinion.

How big?

How much room do you have?  There’s no particular shape of tray necessary; you should keep the ratio of media to nutrient sensible; the nutrient buffers temperature, the media buffers pH, and the tray area drives both.  Unless you want a permanent, fixed installation, keep the size sensible and in accord with the wheels on the trolley.

Don’t you need to be technical?

Nope.  You can be as technical as you want, but if all you want is a basic starter system, even some fundamental tools can be omitted.  With the system we use, for example, we only measure the EC, not the pH.  (EC is the measure of conductivity, or has a correlation to the strength of the nutrient.  pH is a measure of acidity or alkalinity, and is considered the most important measure in professional hydroponics – here we are skipping it because of the acidic media).

How often do I need to check the system?

That will depend upon the size of your tank.  Daily check sound about right; check the water level, the nutrient level and that the pump is running OK.  Going away for a weekend should be fine.  When you know your system you will be in a better position to decide.

Doesn’t hydroponics use chemicals?

Not necessarily.  For example, we avoid the use of sprays or chemicals.  The nutrient is a mix of mineral compounds providing the plant with easy access to all the elements it requires to grow.  Because the plant is not dedicating as much energy to finding the nutrients in the soil it will have a smaller root system and grow more efficiently.  Whilst it is possible to ‘force’ the plant by use of hormones (in hydroponics or in the soil), we prefer to allow the plant to develop naturally, as otherwise the production of essential oil will not keep up – essential oils is what herbs are all about (it’s where the flavour and aroma comes from).

Can I grow wacky herbs in it?

Please – don’t.  It’s probably not a good plan to keep illegal plants in public view, anyway.

 

 

Components

 
Frame:  Wheeled if you are going to move it around.  Big enough for a comfortable working height; wide and deep enough for a reasonable tray; ideally with a shelf for the nutrient tank.  We used a metal computer cabinet picked up cheap at auction; another option was a powder-coated bed stand (with no castors), or perhaps a defunct roll-around table frame.  Look at how to weatherproof it - paint & silicon are the main protectors.
  Tray: You might pick up a UV-resistant PVC tray at a nursery, but the free recycling option is to pick up a styrofoam container at your local supermarket.  Broken is fine, as long as the base is hole-free and there is at least 5 inches of sides all the way around.  A hot wire run from a battery will give you a clean slice, or a box knife will do in a pinch.  Styros last pretty well unless you have attack chickens*.

 
Pump: A *small* mains pump with enough head to run the system.  The cheapest pumps on the market designed for long-life trouble-free operation are fountain and aquarium pumps.  A small submersible fountain pump is fine, and cuts out some plumbing.  However, don’t buy your pump without knowing how high it will pump! You want at least a metre head (the distance the pump will raise water).  You may have to bodge a fitting to the pipe you use.  Remember; silicon caulk is your friend.  You will probably need an extension lead (if you find a pump with a sufficiently long lead this is a lot better than having an extension); secure this under a surface to protect it from rain and in such a way that it doesn’t drop into the tank.  Use a protected power point.
Nutrient Tank: This can be a big as will fit in the frame (it doesn’t have to be full).  Clear or translucent means that you can easily replace water to a mark.  You will need to cut holes in the lid.  If you get flash you could put a float valve on one side; in which case remember to allow for the nutrient in the tank; the valve will be under the nutrient level when the pump is off and everything has flowed back from the tray.  Don’t make the mistake of putting the tank at the bottom of the frame if your pump can’t cut it – Whilst low is better for centre of gravity, putting it higher will give increased flow (putting it too low will give no flow with a weak pump).
Pipework: The minor stuff is drain and line (we used an old plastic tap fitting and a short length of garden hose.  Nutrient feed – buy a cheap kit with half-a-dozen Tees and some 4mm pipe in the irrigation section of your local hardware store.  Have a nose around; there will probably all sorts of shiny bits to tempt you.
EC meter: A cheap EC meter can be had on eBay for forty bucks.  There are meters that operate at different ranges, so check your nutrient.  If you are buying your nutrient from a hydroponic shop they may have something suitable at a reasonable price – go cheap to start.  Know what you want before you lay down your cash.  Don’t buy a pH meter at this point (if at all).  Follow the nutrient guidelines on strength.
Manifold: Make this yourself with poly-pipe and irrigation nozzles.  Keep it simple, secure it well.  The feeds should be close enough together to keep the quincan moist, but don’t overdo it.  Either clamp, tie off or blank the end of the manifold, and fit an appropriate connector to the output pipe from the pump.
Odds & Sods: Perhaps a filter on the pump to avoid grit getting sucked in - the pump types we are talking of are pretty resilient.  A drain for the tray.  Perhaps an inline valve for flow control.  Some clips for holding the pipework in plae would be elegant. 
 
 
Assembly
Make the bed: Cut your tray to size if using an old styro, using hot wire or knife.  Fit the drain to your tray by cut an appropriate hole at one end, bearing in mind that the drain you use needs to be flush with the bottom of the tray and at the tray end to avoid standing water.  A filter to stop the quincan dropping into the tank can be some 4mm mesh.
Mount the tray with a block or wedge under the non-drain end to give a slight tilt to the drain.  You don’t need too much of a slope, just enough to allow the nutrient to run to the drain.  Don’t punch holes in the tray if you can avoid it – it can either rest on the top or you could use locating pegs around it.
Mount the tank: Mount the nutrient tank underneath.  You will need to leave room for access to top up water and nutrient.  The lid should have a drain hole and a nutrient feed hole.  Don't put the tank so low that the pump struggles to raise the nutrient.  If the tank is transparent you can arrange nutrient level marks, but need to provide sun shading to avoid algal bloom.  Otherwise it's a dipstick, a tank meter, or a pitot tube.
Secure the manifold: Make sure the manifold is tied down and cannot spray everywhere.  You could use tape or wire to secure the manifold to the tray.  Run a line to the pump long enough to drop the pump in the tank.  If it gets loose it will empty the tank onto the floor, then trash the pump as it runs dry, so make sure it’s fixed. You may need a valve to adjust the flow rate.
Return line: Run the drain hose into one hole in the tank lid, secure the pump (some fountain pumps come with sucker feet) put some water in the tank to cover, connect the feed line, then turn on.  If all is well, water will come from the head jets, flow down the tray and drain back to the tank.
Treickle or no flow: Your pump lacks grunt.  Either elevate the tank, or get a bigger, better pump.
Jets of nutrient spraying over me: I know you had a fire pump handy, but nozzles flying through the air and embedding themselves in the walls are signs you have over-cooked it.  Either lower the tank, put in a restrictor valve (a two way valve allowing flow return to the tank is another option wuch has benefits) or go down a size of pump.
 
Operation
Initial water trials: Experiment with levels.  Mark up the ‘pump off and fully-drained’ level and the ‘pump on and running’ level, which will be lower (but *not* empty).  If you want to use a float valve, the lower level is the point at which you want water topping-up the tank.  When you are happy, get some 5-10mm quincan; rinse the dust off it, and put a couple of inches into the tray.  Don’t scrub the quincan, you will break it up.  You do want to get the dust off, though, as this will not be good for the impeller.  More quincan isn’t necessarily better, as you will need faster flow/more volume
Measure the system capacity: Mark up the tank level, then drain and measure as you go.   Make up nutrient as required to fill the system plus your refill containers.  Hydroponic Nutrient usually comes in two parts, added equally by volume.  Keep the solutions seperate until mixed in the tank.  You will thus have a full system plus two containers, A & B.
Checking: An EC meter will tell you the electrical conductivity of the nutrient, which is a measure of nutrient strength.  Stronger is not better; too much will burn your plants.  We run at 2.4; your mileage may vary.  Don’t put your meter into either of the A or B undiluted nutrient parts – just the mix in the tank.
Pump timer: The pump should run in the day, turn off at night.  A domestic timer will organize this.  If the quincan is too dry at night you could always arrange a couple of blips in the timer or leave it going. 
Daily routine: One routine is to set the timer to run after your daily check.  Check the tank level and top up with water if required.  Rain water is fine; reticulated water may cause minor problems with salts, depending upon the chlorine levels.  These can be avoided by keeping the tap water in 2 litre soda bottles in the sun (the chlorine will be dissipated).  Then check the EC levels and add nutrient part A & B as required.  Use a measure, mix well, and note the effect on EC.  When you get to know your system you will know how many measures to add without checking.
Checks: KISS.  Is the nutrient flowing? Does it need more water?  Does it need more nutrient?  Are there bugs?  Are there plants?  Remove the former unless beneficial (caterpillers can go to the attack chickens, ladybirds are left in situ.  Snip leaves from the latter as required.  Cultivate a Zen bonsai approach to your miniture garden.
Growing: You can take pot plants, rinse their roots and plant them into the quincan; or put seed straight in.  Try it and see what works for you.  Herbs, apart from being great for cooking, tend to repel some insects – chives are good, for example.  Be careful with Mint – it will try to take over the whole bed using runners.  You could fill a small pot with quincan and bury it in the bed to form a container.  Try aubergines, courgettes, peppers, chillies, herbs.  Keeping a relatively high density will allow the plants to create their own microclimate and cut down on evaporative loss.
 

 
*Attack Chickens.  Ours eat styros.  Go figure.