Hi, I am new to the forum but have been running a system since september 2006. I have a 2000 ltr fish tank which is stocked with 100 Silver Perch, of various size ranging from 100g - 250g.
The water from this tank is pumped to 6 x 600 ltr grow beds which are filled with 10mm gravel. It's a flood drain system with water following back to the fish tank via a main drain. The system is housed in a enviro tunnel.
The system from start up until November 2007 operated as expected, as described by Joel's manual. In November however there was a sudden deterioration in water quality that I have been unable to correct todate despite partial and complete water changes. The water become dark green in less than a week after a complete water change.
The fish on a whole seem healthy, hungery and active but at irregular intervals one or two of the medium or smaller fish will start to swimming to the surface and later swim upside down. At this stage they do try to right themselves but enevitably die. There has been evidence of some reddish marks on some of these fish.
Another factor that may be questionable is a change in feed. They were being fed 2mm Juvenile pellets but around November this was changed to 4mm grower pellets for native fish.
The growing beds have been very productive but at the moment are generally producing herbs that are not as prolic and healthy as last summer.
If anyone could help me out with any advice, I would greatly appreciate it.
Chris
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