I decided I had to have a batch of new fish ready to put in when the big ones are gone. And as Silver Perch are really only available about this time of year I ordered 200 from Silverwater as before. I doubt they would survive with the larger fish so I had to build a new system for the little ones.I have ordered some fibreglass tanks from Murray Hallam in Queensland but he is rather slow to respond to orders so I decided I needed to build a temporary system.
So I cut up one of the 1000 litre IBC's I had bought a year or so ago to try and water shrubs we had planted out on the farm.
Not enough spare water to use them at the moment for the intended purpose anyway.I took a saw to both the steel frame and the plastic container to produce both the fish tank of about 650 litres and the grow bed of about 350 litres from the one IBC. The grow bed needs to be about 300mm deep and that was the reason for the proportions of the split. A system with this size growbed will only support a fairly small fish load but that is the plan anyway- the fish will go to the main system long before the growbed is unable to cope with the nitrogen load.
Then I welded up a support frame for the growbed which enables it to sit over the fishtank.
I also added a pine platform over the steel frame and then several layers of expanded polystyrene foam- mainly to support the odd shape of the old top of the IBC which is now the base of the growbed. I glued the screwoff lid on with silastic and cut 2 drain holes to ensure complete drainage.The growbed sits directly over the fishtank and the drains drop straight into the fish water with drain which are exactly the same as those in the big system.I didn't mention that I also decided it had to be in the conservatory to reduce the likelihood of low temps over winter which I already know are lethal to the fish. In the time we have lived at the farm the lowest temp we have recorded in the conservatory has been about +7 degrees (when it was -7 outside) and the water in the fishtank should not go anywhere near that low point just overnight. And so I shouldn't have to build another solar heater for this setup.
After setting the system up in the front corner of the conservatory I started washing gravel. With the first system I didn't wash the gravel as it was much too big a job and we couldn't afford the water.
This time I didn't want muddy water for a month and I thought it wouldn't be too big a job. Another underestimation. It took me about 3 or 4 hours to wash 300 litres of gravel. Still I did it on the lawn so the water wasn't wasted- that is now the only part of the lawn that doesn't look like straw. I also stole about 50 or 60 litres of gravel from the main system in the belief that that would get the nitrogen cycle started sooner. As it turns out I have an Ammonia level much higher than expected at the moment, in the fingerling system, so perhaps that didn't work as well as it should have.The plan for this growbed is that it will be herb garden and Di had bought the starter plants even before I had washed the gravel- talk about pushy!!
I am using a really neat electronic timer on this system which is currently set up to run for 6 minutes 15 seconds on and 50 minutes off. Both of these times are adjustable to the second and the big benefit is that I don't have to keep the water topped up as carefully to ensure proper flooding of the growbed.
The pump is a pond pump which can move 1000 litres an hour to the head I have on this system and it only draws about 14 watts so the total power usage is very low- much less than the big system which has a pump which draws about 400 watts for 9 minutes in the hour.
The fish arrived last Thursday and look terrific- about 40-50mm long and so far I don't think I have lost a single one which is quite a surprise. And they are hungry and come to the surface to eat unlike their big brothers in the big shed. I think this is because the growbed almost completely shades the fish tank- ie no sun on the water.
I am logging temperatures and water chemistry for this system as well so I will be able to compare the performance of the two systems to some degree.
