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.

A progress report Jan 08

It is now mid January 2008 and the system is working well.
We have had quite a few feeds of sugar snap peas, Tat soi, lettuce and pakchoi.
In fact the first crop of tat soi has all been consumed and a second crop is now on the way as you can see from the picture on the right. The sugar snap peas don't look great but they are still producing a few pods. We will soon be cutting off the plants- planning to leave the roots in the gravel so that they will release the fixed nitrogen back into the system.
Having a little bit of leaf eating grub problems- probably the white cabbage moth- not a major problem yet so I don't think we need to do anything drastic. Any grubs I see will become fish food and that is really just extra protein.

The fish are growing a bit slower than I had expected- now perhaps 60-80mm long and looking very healthy. I have even worked out how to catch some for photo sessions. Used a yabby trap which was simply left on the bottom for a day or so for the fish to become accustomed to it . I then dropped what has become a preferred food- chopped earthworms- into the trap which I lifted quickly out of the water. Caught about 20 or so very vigorous little catties. They now look more like fish than tadpoles. Not hard to see why they are called catfish with those whiskers!

I had thought that I might have had a problem with nitrate levels and this has turned out to be the case. However I was a bit worried that the levels would be too high whereas in fact the level had dropped to almost nil. This would not be a problem if I had a population of large fish. However my fish are very small and the growbeds are quite large and so the fish poo seems to be unable to keep up with the plant's demand for Nitrogen. So I have started adding extra Nitrogen in the form of urea. I bought a box of pure urea from a garden supply centre and have begun to add 4g per day to the fish tank. Apparently fish don't produce urea as most other animals do when they need to excrete Nitrogen. Fish produce ammonia. Fortunately it looks like urea is much less toxic to fish than ammonia and so far this seems to be the case with my fish. I decided on 4 g per day on the basis of it being 1 ppm for the 4000 litres of water. I am assuming the biofilm is converting the urea to ammonia which is then being converted to nitrite and nitrates in the usual way. After a week of adding 4g per day I now have lifted the nitrate level back to about 10ppm while the ammonia level is still Nil.

Despite the potentially low Nitrogen levels the tomatoes planted in November have finally flowered and have begun to set fruit. Still only the size of marbles but I reckon the extra N will get them away and we should be able to start picking tomatoes within a couple of weeks.
This is very exciting as the original plan really was to ensure a tomato crop after the problems we have had in the last couple of drought years in the dirt gardens.
The last picture shows the dozen or so tomato plants. Note the runts on the left of the picture. These were moved just after germination and this was clearly not a good idea. We successfully transplanted tat soi plants but it was probably too much strain for the tomatoes. I will leave the runts in the growbed just to see what happens.
With a bit of luck we might get a late crop.

Veggie production- Tat soi

The fish production in these systems is almost a side product as it will take at least 9 months to produce fish of edible size.
In the mean time we expect to get many kilos of veggies.
The system has only been running for a little over 2 months and already we have eaten a fair few lettuce, pak choi and tat soi plants.
The first seeds actually went in before we got the fish as the system had cycled and there was enough nitrate in the water to support plant growth.
The total growbed area might actually be smaller that optimal for the size of the fish tank- If I find that the nitrates in the water build up to too high a level, (no real idea what that would be at this stage), I will probably add more azolla or duckweed to the fish tank and/or do a partial water change.
We decided not to grow or buy seedlings elsewhere but to simply sprinkle some seeds directly onto the growbed gravel. This seems to work really well- in fact a bit too well as we have had to do quite a bit of thinning once the seeds germinate.
The first picture shows tatsoi about a week after planting and the second shows the same plants after we have eaten the majority of those left in the initial clump and now about to harvest those which were transplanted from the original crowded area. Transplanting set the seedlings back about a week but in effect spread the useful growing season out by an extra week or two. The first picture was taken on 1st October 07 and the second on the 25th November 07 ie total time from planting to almost final crop about 8 weeks. We planted a new lot of seeds about a week ago so should have another harvest of tat soi in about a month.
In the background of the second picture you can see flame lettuce- this was planted about the same time as the initial tat soi but is very congested and probably needs a lot of thinning for individual plants to get away.

Fish

The choice of initial fish was partly determined by what was available and by what species could survive the expected lower temperatures we get here in wintertime.
While I was waiting for the weather to warm up I placed a recording max min thermometer in the fish tank and recorded reasonably stable temperatures in the water. However the low point of 7.5 degrees Celsius means that most of the fish I thought I would like to keep would not be viable.
Help from the Backyard aquaponics forum lead me to decide on Tandanus tandanus ( the Australian eel-tailed catfish) and Bidyanus bidyanus (Australian silver perch).
I remember eating catfish years ago and being very impressed with both flavour and texture so that was a happy discovery. Silver perch is considered one of the really successful species to grow- very hardy and also very good eating.
I managed to find a source of supply for the catfish and so went to the Murray Cod Hatchery at Gumly Gumly , near Wagga,
Murray Cod Hatcheries
RMB 626 Sturt Hwy Wagga Wagga NSW 2650
ph: (02) 6922 7360
and bought 180 fingerlings. They were about 40 to 50mm long at the time. Greg , the owner of the hatchery will possibly have silver perch late this year and if so I plan on buying about 100 little ones then. Greg also reckons they will live quite happily with the catfish without either species wanting to eat the other.

The fish were floated in the tank in the usual way and then when tipped into the water they simply disappeared as the water was so muddy.
This was cause for some concern as I was worried that I couldn't see the fish and so had no idea if they were feeding or not. By the time the water cleared enough for me to see the bottom I was a bit distressed to see a couple of bodies there. I fished out about 10 or 12 dead ones over the next couple of days. I have also removed a couple more since. It is almost impossible to estimate what my actual losses were as the fish are still quite small and difficult to see. Some have grown quite significantly however and there is quite a range of sizes. A few are about four times the body mass of the smallest. I expect uneven growth and it is actually a benefit as it would be a bit of a problem to have all ready for eating at the same time.
At this stage they are feeding on 2.5-3mm sinking pellets for Australian Native fish as the main diet with supplements of live Daphnia and mosquito wrigglers when I can catch the same.

The pictures were taken when the water was muddy and I managed to catch a few who were silly enough to come to the surface. I am no longer able to catch them as they can see the net coming and escape like little rockets.
They look a lot like tadpoles and swim like tadpoles as well.

Initial nitrogen cycle

For the system to work properly it is necessary to establish the bacterial film which will convert the fish waste into something which the plants can utilise.
This film will grow primarily on the surface of the gravel in the growbeds and would have happened naturally without intervention from me. However I wanted this to happen as soon as possible so I took a big sponge filter out of a filter in another fish pond I have and rinsed it out in the water in the big 4000 litre tank. I then got some dead fish we had in the freezer ( flathead fillets and squid which had been forgotten) and suspended this in a couple of nylon bags in the fish tank water for about 3 weeks. I also bought a comprehensive test kit so that I could monitor the progress of the establishment of the cycle.
Unfortunately I clearly missed the peaking of the ammonia production and so don't know how long that took to happen. By the time I got around to testing for all Ammonia , Nitrite and Nitrate the levels of the first two were basically trace to nil. Nitrate was quite high and has remained so ever since. This is not bad as the system had clearly cycled and all ammonia is being converted to nitrate before it has a chance to hurt the fish.