With the recent turn for the better in the weather, we decided it was time to head back out to Carbeth to plant and cycle our gutter system. When we opened the polytunnel door, a completely changed sight met us – everything is shooting up! Beautiful purple broccoli, a small sea of dill, and even a few lemons are making their presence known at the moment.
Carbeth Eco is a hub for sustainability innovation, and they’re testing all sorts of things from optimum wavelengths for plant growth to the soil consistency. But our main focus of the day was on continuing what we had started one cold day in January – our gutter aquaponics system.
We’re starting out with well-established seedlings so that once the system is cycled they’ll be able to absorb the nitrates out of the water for the fish, but we’ll also be starting out some new plants from seed shortly. It’s a good idea to have plants at different stages of growth so that your system maintains steady levels – if all the plants were harvested at the same time, there would be nothing to draw the nitrates out and you could have an algal bloom or a bunch of dead fish on your hands.
We got our hands on some strawberries (Alpine and ‘Cambridge Favourites’), lemon thyme, mint, and peas to start with.
In the next few weeks, as the system becomes more established, we’ll also try sprouting some lettuce from seed – it would be great to have a whole tray of multicoloured salad greens!
Because the plants came in soil, we had to carefully and thoroughly wash the roots before putting it into the system. This is to avoid transferring any unwanted bacteria that might be living in the soil, and to avoid muddying the water.
After that we just slotted the plants in where we want them – as simple as that! We might need to do some rearranging in the coming weeks, but they all have plenty of space to spread out so we’ll see. The mint will no doubt take over soon, but if it becomes too unruly, it can be taken out almost as easily as it was put in, which is one benefit of using the clay substrate.
Finally, we needed something to kick-start the cycling process. We need to build up the bacteria that will convert the ammonia left in the water by the fish into nitrite, and another that will convert the nitrite into nitrate, which can be absorbed by plants. There are several ways of doing this (in the past we’ve used ammonium chloride), but since Carbeth Eco has a trout pond teaming with all the nitro-bacteria your heart could ever desire, we decided to try seeding it naturally. A few minutes of scouting around the pond, and we were able to fish out a brick from the pond. Unconventional, perhaps, but worth a try!
The rest of the work for the moment is up to the bacteria. We added a bit of ammonium chloride for food, but we’ll need to wait for colonies of both types of bacteria to develop before fully introducing our fish. We originally planned on putting trout fingerlings in this system because the pond stocks trout, but because of the heat the polytunnel is already generating, it will be too hot for them. However, tilapia could very well be the perfect new residents for the gutter system – stay tuned!
Recently we’ve been out at Carbeth Eco quite a bit enjoying the countryside and getting to work in their polytunnel imagining up all sorts of designs. Our most recent one is made out of a large fish tank we found in a skip and some guttering – and not much else!
The guttering can often be upcycled, but can be bought for around £13 for a sheath in home DIY shops. We were going for simple and effective with this system. We were able to pick up some gutter clips that did the job perfectly:
While we drilled the gutters straight into the wall of the showcase area behind the tank, a wooden pallet (also easily upcycled, but make sure it wasn’t used to transport hazardous chemicals first) would do nicely for a more portable system. Each row has a slight tilt to it so that the water will flow nicely once the plants have been added.
For this system we decided to have three full rows and a small trough on the bottom, but the gutters could be adjusted to fill as much of the wall as desired. How much area for the grow beds you can use will depend on the amount of water in your tanks, so keep this in mind.
For the moment we’ve stuck netting on the ends to hold in the clay substrate, but we’re going to get gutter caps instead to avoid unwanted water spillage. We also drained a few holes along the bottom of each of the grow beds rows to aid water flow and avoid too much congestion at the ends. We may need to add more once the system is up and running, but the great thing about this design is each tray slides out of its clips, making cleaning, adjusting, and replacement really easy!
What a beaut, eh? We’ll be back in a few weeks to add the end caps, substrate, and plants when things warm up a bit. Carbeth Eco has its own fishery, so we’ll be stocking this guy with some trout fingerlings for the moment, making sure to keep a strong flow of water. Stay tuned for progress!