The present pond filtration strategy is one of an emphsis on low power usage and trying to maximise biological filtration. The pond pump is running on its lowest speed delivering approximately 5200L/hour which equates to just over 2 full turnovers of the 55000 litres contained within the pond per day… The disharge stream is split 3 ways directly at the point of discharge from the pump to achieve that end. One pipe has no flow control valve and feeds a stream directly to the original conventional sand filter. The two remaining flows each have flow control valves to enable the flow rate to be set, albeit coarsely. One stream flows to the Shadehouse Swirl and Bio-Filtration system and the other flows to the adjacent Pump Area Swirl and Bio-Filtration system.
Shadehouse Swirl and Bio-Filtration
This system has a nominal flow rate of 600L/hour and uses 2x200L standard polythene drums and 1x100L trough.
The input stream travels initially in a 40mm pressure pipe but enters a flooded pipe transfer system built using a combination of 90 and 150mm pipe which allows settling and contact time with a biological slime. It then enters via a swirl filter and then passes through the two bio filtration stages. The first stage is a composite of carbon filter foam and polythene mesh rolls.
The second stage is carbon filter foam only. The filtrate continues (by gravity flow) to join the treated water stream as it emerges from the reed bed at the gravel bio filter. Both streams (now combined) continue on to the natural UV settling pond via a short cascade before being returned to the fish pond via another short cascade allowing some oxygen contact.
Pump Area Swirl and Bio-Filtration
This system has a nominal flow rate of 3600L/hour and uses 3x200L polythene drums.
The input stream enters via the swirl filter and then passes through the two polythene swarf bio filtration stages.
The filtrate returns to the fish pond via around 25 metres of upward sloping 90mm pipe where a biological slime coating has more time to contact the stream before being returned to the fish pond via a short cascade allowing some oxygen contact.
Pump Area Sand Filtration and Bio-Filtration
The 55,000L fish pond was once a concrete inground saltwater swimming pool.
The pond pump is the original pool pump and the sand filter was the original filter.
In its present configuration the pump is only ever run at the slowest speed which delivers a total of 5200L/hour. The sand filter only receives approximately 1000L/hour of the total discharge of the pond pump. At this lower flow the sand filter works exceptionally well with quite high sediment loads from the fish waste (aquaponic solution?) stream drawn from the pond skimmer box.
After leaving the sand pump the filtrate is split into two streams. One travels directly to the original pool filter return jets and the other is sent via a 15m x 90mm pipe for a little more biological slime contact time before being returned to the fish pond via a short cascade allowing some oxygen contact.