The carp are here and enjoying their new home. It was slightly surreal coming home to a box of live fish, but after a gentle introduction to our tanks they all swam off happily, showing no ill effects.

We got a couple of kilos of carp food delivered with the fish, but as they’re far more omnivorous than the trout we’re keen to try something a bit more home-grown.

Some of our sumps are doing well at growing duckweed so I thought that would be a good start and added a net-full of duckweed to their tank.

They’re much gentler feeders than the trout, so I haven’t seen them aggressively attacking clumps of weed, but it is steadily disappearing.

At this stage, with tiny digestive systems, they need to be able to “graze” through the day, and I think the duckweed helps with that between their main feedtimes.

As they grow we’ll try to expand their diet further to see if we can eventually produce all their feed in-house – ideally from waste, or areas we’re not using for our food

At some point I’ll manage to document the roller-coaster ride that was our first go at Aquaponics. Suffice to say it was a mixed success – we got to eat lots of delicious trout, but lost quite a few on the way too.

After a major redesign to get the fish out
of the polytunnel we are finally ready to go again – the system has been split to allow for different sizes, and different species, so we’re now eagerly awaiting our first Carp delivery ….

We’ve just got back from a week away, and in our absence the trout were being fed by an automatic fish-feeder. They seem to be pretty happy with that arrangement as they now look huge – at least in comparison to when we left!

We weighed them to see and their weight is now over 35g – doubled in the last two weeks. Time to up the amount we feed them again.

Yesterday we lost our first fish – she got caught up in the net that is over the top of the tank to stop then jumping out!

Feeling a bit sad that we’ve lost one already, but it did give us a chance to weigh and measure one accurately. We’d been working on a weight of about 10g and thought they were about 4″ long. The one who came out is 18g and 4.5″! So now we understand why they were a bit hungrier than expected – we’ve upped their feed from 30g/day to 45g/day (about 1% of body weight). Here’s the pic of the little one who sacrificed herself so that the rest could get properly fed:

They’re a little shy, so no photos yet, but we do have 100 little trout swimming around.

I’ll try and get some pictures when they’ve settled in!

Rainbow trout to be exact! We should be getting tiny (10g) Rainbow trout for our system tomorrow, so I thought it was time for a quick celebratory update:

I’m so flat out planting and working that it’s hard to get to the blog, but I’m taking plenty of pics along the way, so here’s a quick photo update for you:

I know that is an optimistic title for a post, but it feels like we are getting there. Hopefully the leaking sump joints are sealed, and we can get on with it!  Here are the latest pics:

You can see my beautiful brick path – good thermal mass to help with moderating the polytunnel temperatures, and much nicer to walk on than the mud! The large buried sump at the back has a timber deck covering it that the kids can stand on to reach the back beds – so I think those will now be their spot for planting.

And here’s the right hand side:

The timber “paving” is over the new link between the two shallow sumps – designed so that I can lift it up to check for leaks.

Now it’s all “cycling” again – building up the bacteria that’ll clean the water. Soon I’ll start planting – but in the meantime we have our first Aquaponics workshop on next week, so time to tidy up!

Sorry I haven’t been posting much recently – been too busy with aquaponics / filling gaps in house walls & other draftproofing / aquaponics / Transition Town Altrincham, Hale & Bowdon / being on BBC Radio Manchester / changing lightbulbs / saving 1.5 kWh per day by buying a new freezer / aquaponics / and some Christmas and New Year stuff too!

Anyway, let’s resume normal service with a pic from the polytunnel – looks like we might need some heating in there next year:

This is the ice on the top of the fishtank. To give you an idea of scale, the thickest bits are 2-3 inches thick. The water temp is down to 2-3°c and the polytunnel itself got down to -4.5°c at its coldest.

Ok, now this post is going to be really techie, feel free to switch off unless you’ve been passionately following our Aquaponics system development. Before we can put fish into the system we need to make sure that the environment they’re going into is safe for them.

This means it needs to have:

  • The right pH – not too high or too low, it seems 6-8 is about right.
  • Enough Oxygen in the water – Trout need more than 5.5 ppm.
  • No ammonia – any ammonia added needs to be converted into Nitrite & Nitrate by the bacteria in the growbeds.
  • The right temperature – for trout this is less than 25°C and warmer than frozen solid!
  • No chlorine or chloramine (often present in tap water)

With that in mind I set about testing the water that we’d just filled the tanks with – Manchester tap water. If you’re interested, you can see the test results below:

Read the rest of this entry »

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