Aquaponics Silver perch feast

I cant remember if I even mentioned this because I was probably in some kind of deranged pain killer broken rib induced state when it happened, but I may have forgotten to mention I ate one of my big silver perch.

It looked like this.

The South Australian Fisheries people suggest the most humane way (and best way to protect its eating qualities) to dispatch a fish is to plunge it into an ice water slurry, and leave it there.

A few hours later I scaled and cleaned it, and lightly salted it inside and out.




I wrapped it in whatever you call thin plastic kitchen wrap where you live, and left it in the fridge for twelve hours, then cooked it whole.

It was one of the nicest fish I have ever eaten.

Crazy fat.

You cant really tell from this angle, but it was in very fat condition. Looking down from the top, it had that thick section just before its tail like a dolphin.

Most wild caught fish dont seem to have that.

Im guessing its because life is a little tougher in the wild when you dont have an unlimited amount of feed available.

Anyway...

This fish was in very good condition and had excellent fat content.

Apparently silver perch fat is high in Omega 3, but it was mostly delicious.

It weighed 1.08kg gutted and scaled and was 33 cm long.

I wish I had built a much bigger system ages ago so I could have a lot more.

Successfully farming your own protein in only a couple of cubic meters or space is an amazing thing to be able to do in suburbia.

I totally recommend it.



120 Things in 20 years totally recommends it.

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Aeration And Water Movement

 

These plants thrive right above the air stone!  (LINK)

Could this be caused by the movement of water through the roots or is it increased oxygen?  In any case, whether its due to increased oxygen or water movement it is obvious that air stones in the raft tank are quite beneficial.

I asked Forest, my friend and hydroponic guru, if it might be due to water movement.  He felt strongly that its the improved oxygen in the water rather than water movement.  Im still on the fence about that, but Forest really knows about hydroponics so I tend to believe what he says.

But this has gotten me thinking  about adding an aquarium PowerHead and/or incorporating an Under-Gravel Jet System as described at this link.  The Under Gravel Jet appears to be very similar to a Fluidized Sand Filter.  

I found this article about designing a Fluidized Sand Filter.  

Further research shows that they can be designed to remove Nitrates as well as Ammonia and Nitrites.  This of course is not what we would desire in an aquaponic system, but it appears easy enough to avoid removal of Nitrates by not building the filter too deep.

 


Devin uses very large 12" air stones in his raft tanks under the gravel.  Yes he places gravel in the bottom of his Floating Raft tanks.   His results are astounding and I tend to agree with Devin about Rafts vs Gravel beds.   Transplants do better when placed into a raft and growth rates seem to be better, and with good aeration the raft systems can only be improved.

I bought a Hydrofarm Active Air Pump.  
Its a bit noisy but an optional volume control can turn adjust the volume and the noise.

* UPDATE October 10, 2012 -  This Hydrofarm pump has been running 24/7 for 4-1/2 months.  It progressively became louder until it sounded like a jack hammer.  Two days ago I turned it off and replaced it with a new EcoPlus Commercial Air 5.   Even after rebuilding it with parts supplied by the distributor it was no longer working properly.    I have high hopes for the new EcoPlus Commercial Air 5.  It runs much cooler than the Hydrofarm pump which ran so hot I could not even touch .
The new EcoPlus Commercial Air 5. is by no means silent, but it purrs with a low tone rather than a raspy and unpleasant noise. 

The noise was too much so I placed the air pump inside my shop and plumbed the line out to the system

Heres a video about how to repair an air pump

Today I placed four fat air stones in this raft tank under about 4 inches of gravel.

 

Its about time to make some better rafts 8-)

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Aquaponics Aeration

Im planning on buying some trout in the next few days to grow in my aquaponics system, so Im thinking a bit about my oxygen levels.

Toward the end of the trout growing period you have a lot of stuff acting against your trout. Your trout are big and make a lot of waste which depletes oxygen as it breaks down, your trout are big and need lots of oxygen, and your weather is getting warmer,  and warmer water doesnt hold as much gas as colder weather does.

You can test this by opening a warm can of beer, or waiting a few years and watching what happens when the oceans stop absorbing carbon dioxide as they warm up a bit.

Anyway...

I have a tube dumping water from my growbed to my sump.

This much water.

Its not under pressure, but is simply overflowing from the growbed at that height. ie this tubes height regulates the depth of the growbed.

no pressure

The tube stopped a few inches above the water and made some nice splashing and bubbling which I thought was adding some oxygen.

Im probably quite correct in thinking that.

But then I added a tube all the way to the bottom of the tank, and pricked a few holes in the tube just after a narrowing where there was an elbow.

This sucks air into the tube via the Venturi effect.








Apparently, this is because the water experiences higher pressure at the restriction just below the elbow, but then lower pressure when the tube becomes wider again. The result of the low pressure is that it sucks in air.

Which is a little odd.

When you put holes in (or before) the bit thats actually restricted, the holes blow out water.

I know because I checked.

So the result is that oddly enough, air is drawn in and the flow of the water draws it down.

Even more oddly, is that the bubbles dont ever really come out. Some do when the water level is a little low, but these are very small, and not many.

The tube is full of bubbles all in chaos, churning around madly.

It looks like this in real life.

The bubbles enter at the top just where the clear tube starts, and they move all the way to the bottom.

Which is also odd given how gently the water is flowing.





At first I thought they were the same bubbles, but if you block the holes, they clear after a few minutes.

Interesting.

As far as I can tell the air is dissolving.

I have no idea if Im probably quite correct in thinking this.

If gas really does dissolve in water that readily and in that quantity, its no wonder fish can live in the stuff.

I think I just got re-interested in the world.

Perhaps its because I stopped taking all those opiates for my hurty ribs.



120 Things in twenty years  thinks ribs make me less thinky.


[EDIT FROM THE FUTURE - I Thought Id add a link to wikipedias entry on Venturi and now that Ive read it I dont think I have any idea what Im talking about, but what I did clearly works. Im just no longer sure why]

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