Aquaponics and hydroponics

This page is about the system we built and was current until April 2021. We are making big changes over the next two weeks (until early May 2021) and will rewrite this page. Please use it as a bit of history and hopefully, some inspiration and don’t forget to check back in by May to see the new setup!

Both of these ‘ponics’ systems refer to closed loop systems of watering where the water and nutrients are delivered primarily by mechanical means such as pumps. That’s a pretty general definition and there are some exceptions but as a rule, it works.

What’s the difference between Aquaponics and hydroponics?

In hydroponics, the nutrients in the water are added from external sources such as commercial liquid fertilizers. Aquaponics uses these too but the bulk of the nutrients are provided by the waste from the fish that are integrated into the system. Aquaponics relies heavily on bacteria in the system to break down wastes into a plant soluble form. Hydroponics can be run without their inputs.

What is an Aquaponics system?

An aquaponics system is a closed loop system where vegetables or ornamental plants are fed and watered through a closed loop of water circulated by a pump.

How is our system designed?

At Ligaya Garden, our system is currently a a hybrid of aquaponics and hydroponics.

It’s been growing and developing for 5 years now. There’s a bit more of its history on this page if you want to follow it up.

We don’t have enough fish to make it self supporting as we are monitoring the system as it passes into its third year. We reduced the number of fish after a big die off last year and want to run it for a whole year until we add the more expensive eating fish after Summer 2019/2020.

As there are not enough fish to run the system as purely ‘aquaponics’, I add soluble fertilizers at regular intervals. These fertilizers are a mix of seaweed solutions, commercial soluble fertilizers, commercial hydroponics nutrients and home made liquid fertilizers.

Technically, we have three systems, two that are integrated and have grown from each other and a second, stand alone setup.

The smallest one is an approximately 8 metre loop of PVC pipe that is fed from the main fish tank by a small aquarium pump. This drains directly back into the fish tank which is a ‘chopped and flipped’ IBC tank.

The top section of the IBC (the ‘flipped’ bit) holds about 150 litres and is home to a floating raft bed that is used to grow lettuces. This is fed directly from the sump and drains in to the bottom which is the main fish tank.

The main fish tank is the ‘chopped’ bit of the ‘chopped and flipped’ system. It holds about 750 litres of water and is home to the bulk of the fish as well as freshwater mussels for filtration. When the main pump is running, this drains through an external filter and back into the sump.

The sumps are two 250 liter tubs joined by a pipe and valve setup that allows isolation of each part for maintenance. We have two tubs because of the old design of the system which ran directly from the IBC. The build of the frame for the media beds didn’t allow for a single, tall tub of around 500 litres. There are advantages and disadvantages to this layout which I’ll cover later.

The sumps are pumped into the raft beds and the media beds by a single 6000 lph electric pump at a trickling rate. The bulk of the pressure from the pump is sent to the media beds which are 6 plastic drums, cut in half lengthwise and filled with a mix of clay balls and scoria. This scoria was added to the clay balls to compensate for their tendency to float and move when the water in the beds was of a sufficient level. It also adds a huge amount of surface area for the bacteria to live on.

The media beds are where the bulk of the growing takes place. They are fed by a 20 mm PVC pipe with a ball valve for each bed so that water pressure can be adjusted individually. Each bed drains through a Bell Siphon except for the bed furthest from the from the pump which only receives a low flow of water due to the size of the pump and an overall design flaw in the system. This bed is utilised as a constant height, low flow bed for Kang Kong, which thrives on a steady water flow.

These media beds cyclically dump their water directly back into the sump.

Filters and cleaning

Each media bed has a filter of blue aquarium foam where the water enters. I’ve found that the blue material provides the best compromise between filtration and the frequency of cleaning.

The main fish tank feeds in to a bottom fed bucket of filter materials that become finer as the water works its way up to the outlet. This system is preferable to a top fed filter as gravity settles out much of the heavier particles before they reach the finer filter material, reducing clogging. It also reduces that annoying situation where part of the filter is clogged and the rest is affected. or even unused.

In the main fish tank is a small population of freshwater mussels. These actively filter up to 100 litres per day of finer particles from the water. Hopefully, they will breed and multiply so that we can eat them later.

To further clean the system, twice a year, each media bed has its water flow shut off and its outlet pipe separated from the rest of the system. The plants are removed from the beds for seasonal replacement.

The beds are then filled with clean water and the media agitate by hand. The Bell Siphon or stand pipe is then removed, allowing the, now dirty water to be dumped out into buckets. This, nutrient rich water is then distributed around the front garden. The outlet for the bed is then replaced and the bed is allowed to fill to its usual level, then left to stand overnight to settle any remaining sediments before water flow is reestablished and the bed is planted for the new season.

Each bed is individually cleaned in this way in a cycle to reduce any possible shock to the rest of the aquaponics system. Cleaning in this way also reduces the need for a periodic, large scale water replacement that some growers prefer.