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.

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:

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

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:

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!

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.

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:

Ammonia

 This ammonia level has been reached as a result of me adding a lot of domestic ammonia to the system. This is to kick-start the bacteria that we need in the cycling process.

I’m having a bit of trouble picking the reading on this scale, but think it’s probably in the 1.5 ppm range.

pH testing

This seems to be a nice clear result – between 8.5 and 9. That’s a little high, but apparently can be expected to drop as the system ‘cycles’.

Chlorine / Chloramine levels

I was expecting this to be high as I’d only recently topped the tanks up with tap water, however we get a good reading of 0 ppm, which’ll be fine.

Nitrite Levels

The Nitrite level is 0  which we’d expect at this stage, as the bacteria haven’t really had a chance to get going yet. Once the ‘cycling’ starts to work this should start to climb a little.

Dissolved Oxygen

This is  good result – probably about 14 ppm. As we increase the pumping time the aeration should increase too. It’ll be interesting to see how long we can go without a separate air pump.

And final one for the night – the growbeds in place, drainage fittings all complete, and the gravel starting to go in. They are going to need a LOT of gravel – I foresee a week of shifting gravel coming up

There we go – the growbeds on the long side are all done, the drains are all connected, and they’re plumbed in to the fish tank. And we’ve finally taken the plunge – the pump is now running automatically, once an hour:

Now I just need to start keeping an eye on the Ammonia readings to see how our bacteria are going – I guess they’ll be growing VERY slowly this week wth the frost we’ve been having.