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.