Wasabii - cold house

I've been thinking of growing some Wasabii and have been following a thread on Backyard Aquaponics discussing things like the temperature it likes.

It seems it likes to grow in less than 10c water, and less than 25c air.

I'm about to get two solar panels for my epic solar boat adventure, so when they're are not powering the boat, I'll be using them to power my aquaponics system, and I've been thinking of ways to keep the system cool to extend the trout growing season, so perhaps I could use them for that as well.

I ran the problem through the invention engine, and it suggested running coils of hose through a container of water in a fridge as a heat exchange. And connecting the hose to my system. This would obviously cost a lot to run because each time the water went through the growbed, it would collect a stack of heat on a hot day.

But if I put a shade house over the top, I might be able to work something out.

Wasabii likes shade as well, so it should be easy enough to get a couple of layers of that grown up bubble wrap they use for pool covers, and make a tent. Wasabii doesn't grow very tall, so it should only need to be around half a metre high. Perhaps on hinges so it can be lifted when access is required.

I'd add a window so I wouldn't need to let all the heat in whenever I took a peek.



120 Things in 20 years is being told to finish the boat first.

Aquaponics - Cooling a fishtank

I found a source of really inexpensive trout fry from my local fly fishing association, but it's already half way through the trout season, If I were to buy them, ($30 per 100) I'd need a way of cooling my aquaponics system through summer.

A while ago, we had a burst water main in front of our house, and it got me thinking about the possibility of shedding a bit of heat into the water main. Given the foot path is currently dug up, and there are a couple of orange cones alerting people to this fact, it might be possible to run some plastic tubing around the main supply pipe, and pump some of my system water through it.

The temperature of the water and the underground pipe will be roughly the same as the earth around it. If you dig down a few feet. the temperature is much more stable than air temperature in the same location. If you think of a cave, you'll see that the temperature is pretty close to the average yearly temperature of the location. This is because stone (dirt) holds a lot more heat than air, so it takes a lot longer for the rock to change temperature because so much "temperature" can be stored within it.

Because the pipes on my side of my water meter are open to the main pipe running down the length of the street, it might even be possible to use the pipes within my property.

It's just a vague thought, but it was in my head, so it had to come out.


120 things in 20 years just thought of something else, but it's too naughty to post about.

Aquaponics - Fish stocking density

So...

1 fish @ 500g per 20L of filtration, or 2.5% of the media in fishmeat by volume (fish being neutrally buoyant equal water weight by volume  (1 ml of water = 1g) seems like a reasonably common stocking level.

...

So for every 20 L of growbed media (gravel, clay balls etc) you can stock 1 fish that you intend to grow out to plate size.

Plate size is considered to be 500g, and reflects what a restaurant might like to serve a customer on a plate rather than the actual size of your plate.

I dont know what size your plate is.

Although it's probably, by coincidence, roughly the same length as a "plate sized fish" wide.

Or high.

Anyway...

So a fish, that looks nice on a dinner plate, is around 30cm long, weighs around 500g, or a little over a pound,  and requires around 20L or 5 ¼ gallons of filtration or grow media to support it throughout it's life of pumping fish crud into the water.

“Stop eating so much. You don't need that much protein in one meal.” I sometimes tell myself. But I'm wrong. Fish is delicious, so I'm probably going to keep eating that much.

So you put a stack of fish into your system, and you end up waiting quite a while, then you pull them all out, and put them in the freezer.

But fresh is best.

Why don't we eat smaller fish? Fish are crazy brave when they are young, and feed like mad taking all kinds of risks to get to the food before their fellow fishies.  This means they grow quite quickly when they are young.

Trout and barramundi seem to grow to plate size in 8 months. But that might be because they are already quite grown up when you get them. Silver perch take around  two years. Or actually two summers, as they dont feed a lot during winter. Most fish varieties grow quite fast at their preferred temperature.

So if our systems need the number of fish they can support to give the vegies their best conditions to impress, why do we have so few fish for so long.

Most people stock a number of fish that their system can cope with once they have grown to plate size. But that means the system is low on nutrients for the greater part of a year, and then perhaps overloaded for a bit, then suddenly, has no nutrients for the plants at all when the fish are all harvested.

The system's resident veggies must hate it.

But what this means is that you either have to supplement your ammonia, or nitrate inputs into the system with Charlie Carp (fishy goo) or something to keep the plants happy.

So, all that stuff is true.

But its also true that we eat fish that are smaller then a plate sized trout. Sometimes a lot smaller.

In South Australia, where I happen to be, we eat Australian Herring, Gar Fish, Leather Jacket, Yellow Fin Whiting, and almost every other fish we eat can be bought or legally caught at smaller than plate size. I think even our King Gorge Whiting, considered by many as one of the greats, are legally caught at less that “plate size”.

So what's so good about plate size?

Don't answer that, it's a rhetorical question. Unless there is actually an answer...

then …

go for it.

But...

Ideally we should stock our systems with 100% of their fish meat holding capacity, and start eating the biggest of the small fish the following week.

That could get a little finicky when trying to fillet a 4cm fingerling, but perhaps there is some kind of compromise.

Silver perch take two summers to reach plate size.

Perhaps we should stock an amount of silver perch, such that after one summer, there is enough fish by weight, that we are not over stocked, but that we can start eating. They grow slowly in the colder time, but that might mean we can slowly eat some in an attempt to keep the stocking level at close to optimum, and when the next summer comes, we still have the right amount of fish, but we can start eating more, more often, until we find ourselves with one last megafish, still capable of running the system.

Obviously rather than one mega fish, it would be better to buy more fry at a time when the system could afford ...say... 50 new fish, if there was one less big one in the system.

That should be the trigger for buying new fish.

After working out how many fish such a program would require to restock, approximate the big fish equivalent to the number of new fry, and restock when eating the big fish would allow enough filtration media, to buy a new batch of small fish.

This might seem obvious to some, but it doesn't seem to be normal practice.

Given the price of decent quality, ethically raised, organic, un-polluted, un-heavy metalled, fish, and the feed conversion rate of around 1:1.2 (ie 1.2 kg of feed makes around 1kg of fish (insects, algae etc make up some feed, and fish do a whole lot of floating perfectly still waiting for food to wander past them, so they are fantastically efficient(some trials have shown better than a 1:1 ratio))) …

where was I...

Given all that, and the fact that you pay a bit for your new little fish (around $1.80 for me) it still works out to be an exxcellent deal to eat the fish way before they are plate sized.

So...

I think I should try to work out how many fish I should buy to make this form of stocking a reality.




120 Things in 20 years needs to make a spreadsheet to work out a better aquaponics fish stocking density plan. Or just take a bit of an educated guess.

Aquaponics - Fish

Aquaponics - Fish

Fish! Vegetarians, this page might not be for you.

The swimmy, tasty side of the aquaponics equation is fish. Depending on where you live there are a few different options. Talapia might be one if you don't live in Australia. Statistically you don't live in Australia. If you did live in Australia, and you grew talapia, you might get into a stack of trouble. Talapia are a pest species for all of the reasons that make them a good candidate for aquaponics.

Catfish. I know nothing about catfish but it seems like they are a candidate for aquaponics. Other species that might be worth a look are Cod (angry, eat their young), Barramundi (warm water), Jade perch (highest omega three), Goldfish (only swallowed whole by 50's youth in TV sitcom "Happy Days") and various things like clams, and walking things with claws(whatever they may be called in your part of the world). Basically, from what I've read, if it poops and lives in fresh water you can use it. But if you don't intend to eat it I would think goldfish would be your best bet.

Check your local laws, but good candidates for edible species include...

Talapia are a very popular fish to grow in an aquaponics system because they cope with a wide range of water conditions, they eat everything and are apparently good to eat, they breed readily and grow quickly. If they are legal in your area, from what I've read they seem like the best choice as long as you have warm water. Talapia covert food into fish very efficiently.

Trout. If you are in a colder part of the globe you might try trout. Trout enjoy water that's less than 20 deg C. Its often possible to grow trout as a winter crop as they grow very quickly. Trout are often farmed commercially and are known for their conversion rate of feed to harvested fish fillets. ie It takes a relatively small amount of feed to grow a trout. I think that's because they do a lot of sitting still.

Carp are another pest species for Australians so are a no-go area for me. They are full of bones and taste like mud. Many Australians have a poor relationship with carp because we think they are full of bones and taste like mud. Australians also thought they tasted so good that they would import them from Europe and release them into waterways, causing insane damage to eco-systems that were poised on a knife-edge of sustainability just by virtue of being in Australia. Full of bones, mud.


Yabby. The yabby is delicious. As are marron. I'll be trying to grow some yabbies and/or some marron.
They breed in captivity, eat scraps of food left by other fish, and generally clean up your fish tank. I am trying to work out a way to keep them separate but living in the same fish tank.

[more in this post on marron]

Silver perch. Silver Perch seem to be the most suitable species for me to grow based on my location. They are good to eat but are a little slow to grow. They have high levels of omega three fatty acids, whilst retaining a clean white flesh. They are omnivores, and will eat things like lettuce and duckweed (a very small, floating plant I'll try to grow in nutrient rich barrels of water for fish food) From what I can gather they can take a wide range of water temperatures but might not grow much over winter. They also tolerate a wide range of water pH. If all goes well, I should have fish for the plate within 18 months, and then have a constant supply after that. Silver perch seem to get along with little silver perch without all the cannibalism that comes with some other species so I'm hoping to keep 3 or 4 different ages of silvers all in the same tank.

Not just Aquaponics - Fish, http://120thingsin20years.blogspot.com