Top up water

As the growbeds are not fully planted, and the area is really a glasshouse, a fair bit of water evaporates each day. The growbeds get quite hot to touch in the middle of the day which clearly accentuates the problem. .
To keep the system running well and to ensure the plants get adequate water top up water is needed fairly often- really about every couple of days. The plan is to fill the growbeds to within a couple of centimetres of the top of the gravel each flood cycle.
I have a 20000 litre rainwater tank collecting the water from the shed and I have run a pipe from that tank to just over the fish tank.
Up until the addition of the top up barrel I simply opened the big white gate valve and ran in water for a short while. The problem with that arrangement was that I didn't know how much water I was adding and more importantly on one occasion I forgot the water was running for about 10 minutes and ended up adding far too much. I didn't overflow the fish tank but I did have to reset the float switch which was a pain.
So I have added a 200 litre blue barrel which has a sight tube which enables me to add, and record, an accurate volume of water when needed. At this stage it looks like I need 50 litres every second day. I doubt that I will need to add anything like this much in the cooler months but it is still likely that the extra water needed over a year could be as much as 7000 to 9000 litres. We have had a fairly wet last couple of months and the 20000 litre tank is still full so that much water will not be problem. Posts to several of the online aquaponics groups suggest that an aquaponics setup uses only about 10% of the water of a dirt garden. I have no idea if that is true but I do know that we had real trouble with enough water for our dirt garden the last couple of years wheras we look like having no trouble with water with this new venture.

Azolla production

I have been reading all sorts of good things about the food value, for fish, of the water fern azolla. It contains quite a lot of protein in the dried state and has been used in lots of places around the world as a protein supplement in livestock production. The most interesting thing about azolla is that it can double its mass every few days when provided with the right conditions. I had a few failures in trying to get a culture going but am now producing quite respectable quantities on a daily basis. This is scooped out of the pond and dried on a rack which is simply flyscreen over a bit of steel mesh. After a day or so of drying I rub it through a sieve and now have about 9 or 10 litres of dried leaf. As the water content of the living plant is about 95% the 10 litres of dried leaf represents probably 200 litres of fresh azolla. And that was all produced in the 1200 litre stock trough outside the shed over about a month or so. This little plant grows like a weed when given the right conditions.
To start the culture the trough was half filled with water and a couple of biscuits of hay and a handful of super phosphate was added. This creates an algal bloom which was actually planned as a starter food source for mosquito wrigglers and daphnia. I got quite a few feeds of wrigglers and daphnia for the fish but then in a moment of weakness chucked in a few handfuls of azolla. The water in the trough became so covered with azolla that I no longer get a harvest of live food for the fish.

So I have now created a new area where I can grow azolla and this will free up the big trough for live food production. The dried leaf will become one of the ingredients of my homemade fish food - more about that later.

The new area is made up of 6 half blue barrels each of 100 litres - the total volume is about 600 litres and the total surface area is about 3 square metres. These have been seeded with hay and/or super and should be going green within a few days . I plan to start adding chicken litter and droppings in the new areas as an experiment. The overall plan is for as many of the inputs to the system to be home grown- sort of a permaculture system where one areas waste is another areas nutrient.

The pieces of shadecloth in the water are there to give lizards, which seem to want to get into the barrels all the time, something to climb out on. Before the shadecloth went in I inadvertently trapped several of the Cunninghams skinks which live near the shed. Fortunately the water was not deep enough at the time to drown them and they survived.

More fish

A couple of days ago I received a delivery of 100 Silver Perch fingerlings . These were part of the original plan but were not available until last week.
They came from
Ian Charles at
Silverwater Native Fish , Old Wagga Rd, Grong Grong NSW 2652 ph (02) 69562122.

A really nice bloke to deal with. I had a chat with him as he was delivering live plate size Silver perch to a Chinese restaurant in Jamison. He transports the big fish in a heavily insulated box with a pure oxygen bubbler. The fish are partially anaesthetised by adding a small amount of clove oil to the water. He had about 90 fish weighing between 600g and 1 kilo in a 400litre box- all quite happy - but very crowded.

My fish were a lot smaller- between 40mm and 80mm. Unfortunately about 20 died in the first couple of days but the deaths have stopped and the fish now look fat and healthy.
They spend most of their time in the middle water unlike the cats which are mostly on the bottom. Like the cats they are very fond of chopped earthworms and when feeding seem to encourage the cats to move higher up in the water. The cats will have to eat faster if they are to get their share of the worms. Worms are a treat- the primary food at this stage is a sinking pellet food which although Australian made is made from imported fish meal so I plan on making my own fish food in the not to distant future.
I suspect that the silvers will grow a fair bit faster than the cats so we might be having fish dinners late this year with a bit of luck.