In late May 2009, we launched our new Integrated Backyard Food Production site - www.microponics.net.au.  If you liked this site, you'll probably like the new site, too.

While summer technically ended about a week ago, the hot humid weather and insects clearly haven't got the message so, while we wait for autumn to really arrive, I decided to conduct a continuous flow experiment using my grow beds.

Continuous flow media-based systems usually comprise a watering grid which delivers nutrient rich water from the fish tank to the root zone of the plants.  The water percolates down through the media before draining back into the fish tank.  This regime can be very effective.

The recent 2009 Aquaponics Course Seminar included a field trip that featured a small continuous flow set up.  This system was different inasmuch as it was a combination of deep water cycle grow tanks and media-based grow beds.  The beds were filled with expanded clay media.  The water level was maintained at about 50mm below the surface of the media.

The fish plants in the system were obviously healthy and the water in the fish tank was crystal clear.

While our 4 tank system is excellent for Jade perch, water quality appears to be an issue for our Murray cod and Barramundi.....particularly at the feeding rates that I'd like to achieve.   Our use of auto-syphons (and the way that they stir the water up) is exacerbating our water quality problem.

Replicating the continuous flow (continuously flooded) arrangement was as simple as removing the auto-syphon cores from my seven grow beds.

The beds have flooded up and remain full...overflowing down the standpipe.  Rather cascading back into the tank at periodic intervals (as is the case with auto-syphons), the water now drains back into the fish tank continuously.

The media in this continuous flow arrangement is going to require cleaning periodically but our use of expanded clay will make that an easy task. 

The desired outcomes for this experiment include:

• more effective solids settling
• denitrification - producing mineralisation of settled solids
• effective nitrification
• good plant growth

Some of the prospective issues include:

• nitrification - I normally prefer the percolating action of trickling or flood and drain bio-filters.
• aeration - I've got good diffusers in each of the fish tanks.
• solids build up - will need to be removed eventually.

We may have up to a month to go before we begin to experience optimum plant growing conditions in our our region.  Hopefully, that will be sufficient time to give us some insight into the effectiveness of this type of continuous flow arrangement.

Welcome to our new Redclaw nursery.

We removed our Redclaw female from the small aquarium in which she'd been kept while her eggs hatched out.  She went into a fish tank with our half-grown Jade Perch.....the least risky option (for her and for fish).

We then transferred the juvenile Redclaw into their new home.

The weighted plastic tray will be used as a feeding point and it also anchors the four air lines that ensure adequate aeration.  The plastic onion sacks provide a secure environment for the tiny crustaceans to undergo the many moults that will be necessary between now and when they reach harvest size.

The Black Soldier Fly larvae in my BioPod have been churning through every bit of food I can send their way.  For some reason, however, the volume of food that I'm giving the larvae isn't reflected in the numbers that appear in the collection chamber.   While there are many thousands in the composting chamber, I find that, some days, I get to harvest very few.

Bio-conversion is one thing but I want animal protein, too......so I've started taking larvae directly from the composting chamber.  I use a small potting spade and scoop up a handful and throw them on the ground for the chickens.   This practice doesn't seem to be impacting their numbers in any way and it ensures that I get a useful daily harvest, too.

In coming weeks, I'm going to increase the amount that I harvest directly so that I can build up my frozen stocks. 

My duckweed has been growing so quickly that I'd run out of things to do with it.....and then I decided to feed it to the BSF larvae.  They consumed a bucketful in about 24 hours.....and revealed one more use for this incredible little plant. 

Yesterday, we had what 1960's iconic wierdo Tiny Tim described as a "blessed event".....our female Redclaw hatched her babies.

After days of watching, I shone the torch into her glass nursery and there they were.......hundreds of them. Each one is a tiny full-formed replica of their mother.

Now we have to determine how long Mum gets to stay with the babies so that we can remove her to prevent her snacking on them.  Life springs eternal.

A couple of weeks ago, we planted out a heap of seedlings into our aquaponic grow beds and our square foot bed.  Most of the seedlings in the grow beds withered.  Those in the square foot bed are kicking along nicely.  Heat, humidity and bugs make this a hapless time for growing plants aquaponically.

The 40lpm air pump that aerates our fish tank failed a couple of days ago. I've replaced it with a 200lpm air blower......and we've got four new air diffusers coming, too.  I'm keen to get a lot more air into my tanks as part of a cost effective push toward much better water quality.

I've inserted a leaf catcher arrangement into one of my 235 litre grow beds to help trap fish wastes.  I've lined it with a piece of dacron in an attempt to clear up the water in my Jade perch tanks.  Rinsing out the dacron twice a day is not my idea of a long term solids removal solution but it's a start.

About two weeks ago, we removed the fish from one of the four tanks that comprise our new Aquaponics set up.  I shut off the air to the tank but left the pump running so the grow beds continued to flood and drain.

While the tank is still being aerated by the water cascading back into the fish tank from the grow beds, I've been interested to note the amount of solid waste that has settled out.  I've syphoned it off on three occasions but it continues to build up.

I advocate the removal of solids from aquaponics systems (including those with media-based grow beds) on the grounds that solids impair nitrification which has a negative impact on water quality.  The presence of solids also encourages denitrification which drives the pH up. 

What I didn't realise (before transferring the fish from the tank) is exactly how much solid waste is in suspension.

Advocates of media-based grow beds claim that worms will mineralise the fish solids and release the nutrients that are bound up in them.  While this may be true (and I agree that the nutrients should be put back into the system), I'm of the view that mineralising them in the grow beds is probably not the best way to do it.

As things currently stand, I'm limited in the amount of food that I can give to my fish which impacts their growth rate.....so I've resolved to increase the aeration to the tanks and to experiment with various solids removal devices.

A visitor to Creek Street Micro Farm brought us five Redclaw, one of which was berried female (carrying eggs).

We set up an aquarium home for the expectant mum.  We're told that her eggs about 10 days away from hatching.  Once they've hatched, we'll keep the Redclaw fry in the aquarium for a few days before releasing them into our duckweed tank to grow out.

I've always wanted to breed and rear freshwater crayfish but I was under the impression that their aggressive behaviour toward one another meant that they needed plenty of space.  This is difficult to provide in tanks which is why freshwater crayfish like yabbies and redclaw are usually grown out in ponds.

Our visitor, who knows a lot about freshwater crayfish, has undertaken to teach us more about these intriguing creatures.....to the point where we can produce sufficient of them to meet our own needs.

The remaining crayfish (which were too large to be used for breeding) went into the freezer to kill them before boiling them in some salted water.  We ate them....and they were good, too.

My records reveal that we first planted out our 4 tank system exactly eight weeks ago. 

Within the first month, we harvested lots of lettuce, herbs and Asian greens.  We've been picking cucumbers since Week 5....and we began harvesting tomatoes a week ago.

Given that this is the worst time of the year to grow food in SE Queensland, and that our system is still very young, I'm delighted with how things are going.