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Swimming pool conversion to aquaculture

Prompted by increasing environmental awareness, diminishing demand for the use of the swimming pool after the kids left home, and the exorbitant price of fish - the idea for converting our swimming pool into an aquaponics system started to take shape. Having a neighbour who was already into this movement was an added advantage, but I couldn't find too much information on people who were converting their swimming pools into these types of systems - most people bought standard sized units from professional aquaponics suppliers which were efficient but frankly very ugly and not very nice environments for the animals (fish).

 

We started out with a relatively small pool about 25,000 litres.  The first thing I did was drain the pool.

I then got a load of local river sand - approximately 15 cubic metres and distributed that into the bottom of the pool to reduce its size to around half the volume.  I also created a bund at one end (a river sand wall), which I wanted to use to section off from the fish an area for water plants which I'd read were usually destroyed by larger fish.

As well as filtering the water through the standard grow beds (3), I decided that the volume of water was large enough to warrant additional filtration and the cheapest method to do this was to incorporate a section of the pool as a gravel filter itself.

This section lay behind the sand bund and water would be filtered from the open section of the pond through pipes (on their way to the external grow beds - through a one way valve and out 6mm holes - 10 cm apart) at the bottom of this section.

This in- pool filter would house the water plants and nutrients would feed up through the gravel to the plant roots. I've seen similar ideas in swimming pools where people wanted to avoid chlorine or salt filters.

Previous to the introduction of the aquaponics system, I had a productive vegetable garden of approximately 60 square metres. The idea of the aquaponics is to compensate for a loss of much of this garden in the summer months when water is scarce.

Initially I looked at building my own beds but given my work commitments and 'lets get it done' attitude, I settled on ready made beds. I sourced one from a local pool manufacturer and two other units from the local supplier. Both units were made from stabilised PVC.

One unit [left ] was to be positioned just above pool height inside the pool enclosure whilst the other two [see below] were to be housed on the old veggie garden site and raised for easier access.  The old veggie garden site is approx. 6 metres from the pool edge and I had to run piping under the pool fence and paving.

The drainage from these three units would return via a common exit line out the existing pool ducts. That was the original plan, but there were a couple of hiccups!

The grow beds were planted about a week ago with a range of vegetables - lettuce, Chinese greens, capsicum, cucumber and rhubarb. The grow bed closest to the pond we have reserved for strawberries. We have put in a few native minnows to start with and plan to stock the pool with our first lot of fish and marron (local fresh water crayfish)  in the New Year.

This seems to be a constant source of discussion on aquaponics blogs and there are lots of arguments to favour different types of mediums. After a while I settled on local pea gravel (10cm diameter), more than anything it was price. The whole system was starting to eat into the hip pocket - especially after purchasing the grow beds. My neighbour and consultant also used the pea gravel in one of his grow beds with good results. I'd also got a handful and tested the PH to ensure it didn't contain anything that might negatively effect the water quality.

I got a tip on washing the gravel off a local forum and bought an old fly-wire door, which we shovelled the gravel onto in small lots before hosing it down. The washed gravel was then emptied into a wheel barrow and carted off to the grow beds.

Well this was a bit like the grow media issue - lots of varying opinion leaving me having to trust my own judgment.  Given the volume of the pool (now approx. 15,000 litres) and the need to filter that every 2 hours to keep the water quality high enough for some of the more temperamental fish species (i.e. trout), I was looking for something that could move a fair volume of water. I also had a fair amount of distance to cover with two of the three external grow beds about 6 metres away from the pool and at least 2 metres higher than where the pump sits.

The other reason I wanted a stronger than average pump was because I hoped to divert a percentage of the water away from the grow beds and return that to the pool via a large pipe running off a nearby pergola. This was a little piece of drama inspired during a recent visit to Spain where water gardens and water features are truly spectacular.

Anyway the end result was that the pump carried sufficient water to the three grow beds but not the arching aerator - I believe it is pumping well below its specifications and I plan to remedy that in the new year. In the meantime the return from the grow beds is  aerating the water but on a smaller scale.

We also planted the in-pool grow bed with a selection of water lily's, water iris and native sedges. These have responded very happily to their new environment and we had the first lily flower last week.

The final steps in the project have been to add landscaping around the edges of the pool which over time will add to its natural look. The pond itself is clear and has become a haven for local wildlife. Already it is full of tadpoles, buzzing with colourful dragonflies. I have covered the river sand with a thin layer of finely crushed quartz and it's a very inviting environment. The plan is to still be able to wade in and cool off on those really hot summer days and I think this should be OK.

NOTE: This is a guide to a hit and miss, handy-man, swimming pool conversion to acquaponics set up. I thought I'd write this up so others thinking of doing the same thing could see what might work and what might not.

This project began around the middle of the 2010 calendar year after my neighbour handed me one of 48 Barramundi he had harvested from his standardised acquaponics set up next door. Not long after the government announced severe water restrictions, after a winter of virtually no rain, and keen vegetable growers like myself faced the prospect of having to pull up our gardens over the summer. An aquaponics system seemed like a way to solve a number of issues - including what to do with your swimming pool when the kids have left home and it gets little use. How to water your vegetables in the face of severe water restrictions, and how to afford fish when the cost keeps skyrocketing.

Many thanks to Simon for sharing his project. I am sure there are many pool owners out there that have given consideration to filling in a swimming pool