Just a few snaps from Yesterday’s work evening – we decided our donated / rescued crayfish should go aquaponic – so re-vived our fishplant system (minus siphon and plus timer)! Oh and Sam dabbled with the KijaniGrows system… We are looking forward to connecting up the Seneye monitoring system and getting some plants in there next time!

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Yey the fish harvest has started! I have taken 6 (10% of total of 61) Tilapia from the tank & they averaged 200g each! Although they are plate sized my research tells me an average fish size should be 450g. There are some bigger ones in the tank they were just to fast to catch, there are also lots of smaller ones as well. I needed to have less fish in the tank because the nitrite/nitrate levels were getting to high to regularly. So I have frozen them & will collect more until I have enough to feed everybody who volunteered there time & energy making the Bristol Fish Project happen. I have a field kitchen & am willing to pull up in a green space in Bristol & cook up a picnic for all those who wish to chow down on this amazingly hardy fish (I wonder what they taste like?) Tilapia were the most farmed fish in 2012 so I find it strange that no one in the UK has heard of them. Anyways anybody is welcome to come & see the setup in the shop! Contact me first to make sure I am in.

So here’s an update on the system, contact me if you have any questions or want to come and see the setup.

So this little vid shows the fish in more detail & not so blurry because there not feeding, you can see there looking good! Will upload another video regarding the set up later today!

Just a little video so you can see the fish, http://www.youtube.com/watch?v=XjLh9Jg07qQ. Having a problem with the small bell syphon I have added in the new flood & drain system. It keeps not working. Seems you have to have just the right amount of water coming into the growing bed? To little & the syphon wont kick in! To much & it wont stop! I’m thinking that the delivery tubes to the NFT will have to be changed as they are rather small & could be blocked up quite easily! As for the fish they are starting to grow recognisably into Tilapia with the head almost dropping down to the front of their bodies.

Sorry I had to correct a couple of points in the video, so here it is re-uploaded

This winter, albeit mild has been a hard one for the fish project! Here we talk about our main challenges chosen solutions and share photos:

In November, the tanks which we had maintained at 24 degrees during the dropping temperatures of late October were no longer holding that temperature over night and gradually in one of our tanks (which runs on overflow from another) we were seeing a drop towards 22… and then at its worst 19 degrees. The tilapia in that tank were sluggish and not feeding well and we could see that their immuno-response was reduced as every few days one would be lost to streptococcus – a naturally occurring bacteria that overwhelms fish when they are weak and causes haemorrhaging in the anus as shown in the photo. We decided to add more water to the polytunnel to increase thermal mass, in the hope that the heat we did add to the system wouldn’t be lost too rapidly. Then we further insulated the tanks with a rockwool layer fixed with pallet wrap, added mini polytunnels over the tanks, and we bubble wrapped the polytunnel – it worked – adding a few degrees to the tank temperatures, but was ugly and dripping – a post apocalyptic, Aldous Huxley nightmare… Continue reading →

So much has been happening! We’ve doubled the system’s capacity, and are still fighting to maintain a decent growing temperature in the tanks. This week Daniel and Katrien visited us from Belgium – and kindly took some pictures 🙂

Micky and Daniel level the pipes to the grow beds.

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Signs of Iron Deficiency in the Mizuna

We’ve started to notice our plants getting lighter green and veins appearing on the leaves – we’ve got a nutrient deficiency on our hands… Working with an aquaponic system – particularly a young system, is a balancing act. The fish produce waste, bacteria break this down and then plants absorb the nitrates, and macro /micro nutrients. The ease at which nutrients can be absorbed by the plants is affected by the pH of the water. In our system the pH has been a little bit high for the nutrients to be in a form the plants can readily absorb. Bristol has very hard water – pH 7.4 in our tanks.  We’re using peat pellets to try to slightly acidify the system. Seems to be working – pH readings today were down to pH7.2 today.

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James came in last week, to hammer, stretch and stick together a flying net for ‘fly world’ –  a cosy home for our resident black soldier fly larvae. Black soldier flies mate in flight – the net cage you can see in the picture that James is so proudly showing us is in effect the ‘mile high’ club for our flies.

We’re setting the system up so that the larvae self-harvest when they are ready to turn into flies. They crawl out of the biodigestion unit where we put the waste food, and drop into another unit – there we will be deciding which ones to let develop into flies, and which to use in the fish feed.

At home the larvae are eating their way through spent grain from a local Brewery, and other food waste that we can chuck in. No sign of any flies yet – though we’ve only just started incubating the mix to a balmy 30 degrees. Hopefully the return to the polytunnel which in this shabby weather is rather less cosy won’t slow them down too much!

We are now monitoring the water temperature in the first of our 2 700L – ish tanks. Today’s max water temp was around 30 degrees, with around 49 degrees max recorded inside the polytunnel! – Will be interesting to see how low or high the water temperature will get in the next few days.

We are working on reducing the temperature ‘swings’ by increasing thermal mass in the polytunnel, if we get our desired 8 tanks, we should be getting towards a much stable environment for our plants and fish!

The next problem is shading – how to keep the plants from bolting or shriveling up under the hot hot sun! Watch this space for our attempts at stabilising our little ecosystem!