Hydraulic loading of filter = 5 to 10 m/hr ( a 2.2m diam filter, surface area = 3.8 m2, water flow = 19 to 38 m3/hr
Aquarium turn-over rate through filter = once every 1 to 2 times per weeks depends upon biomass loading and nitrate production, but 2 tonnes of fish will require approximately 1 cubic metre of filter media of DFM and Magphlow at a ratio of 1 : 2 So 10 tonnes of fish require approx 5 tonnes of media, of which 1.5 tonnes is DMF and 2.5 tonnes is MagPhlow. Media consumption for 10 tonnes biomass of fish will be approx 25 kg /week of DMF and 50 kg /week of MagPhlow. The filter should be topped up with media once a month.
Bed depth = 1.2mWater Flow = 5 to 10 cubic metres per hour per square meter of filter bed surface area.
Example, 2.2m diam filter = 3.8 m2 surface area = water flow of 19 to 38 cubic metres per hour.
Filter bed make-up = bed depth 1200mm,
100mm of grade 3 afm on base of filter, 100 mm grade 2 AFM on top of the grade 3, then layer the filter with 1 x 25 kg bag of DFM followed by 2 x 25 kg bags of MagpHlow media, until the bed depth of media in total is 1200mm, the bulk bed density is AFM is 1.25 to 1, the bulk bed density of DFM and Magphlow may be taken as 1.1 to 1.
Example calculation.
Aquaculture system volume = 2000 cubic meters
Biomass loading of fish 5 kg per cubic metre of water = 10 tonnes biomass
Normally we aim to pass all of the water in the system through the DMF media once or twice a week. Given that the water volume is 2000 cubic meters, then in order to filter this water once a week
2000/24 / 7 = 11.9 to 22 cubic metres per hour.
The hydraulic loading is a maximum of 5 to 10m/hr, but you need to treat 22cubm/hr the filter should have a surface area of 4 square meters. If you use 2.2m diam filter with a surface area of 4 square meter, or you may use 4 x 1.1m diam filters. The filters are back-washed at a rate of approx 40 m/hr so for a 4 square meter filter, the back-wash rate is 4 x 40 = 160 cubm/hr. The back-wash duration should only be for about 2 minutes once or twice a week, so only about 6 cubic metres of water will be used for a 2.2m diam filter.
Maintenance
The Dryden Aqua DFM system requires virtually no maintenance, however the Magphlow media and DFM media are slowly consumed by the bacteria in relation to the amount of nitrate removed, so you will occasionally need to add more of the product to the top of the filter bed. Add the product in proportions 1 : 2, that is 1 x 25 kg bag of sulphur DFM media and 2 x 25 kg sacks of Magphlow media. The rate at which it is required depends upon the production of nitrate, if you know this figure then you can work out how much media will be used from the following;
When 1 g of Nitrate is removed by the bacteria 2.5 g of sulphate are produced, the sulphate will then continue to increase in the water, however sulphate is already present in marine systems at a very high concentration ( click here for seawater analysis). 1 g of nitrate removed consumes 1 g of DNF (sulphur) media and approx 2 grams of MagPhlow media, and will produce 0.7 grams of bacteria cell biomass
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