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Sizing a Bead Filter
On average the conversion rate of ammonia to nitrate is as follows: 1 cubic foot of beads converts the ammonia released from 1 lb of 35% protein fish food daily. i.e. 100lbs of fish requires 1 cubic foot of beads to convert the ammonia produced by the koi and gold fish.
Table 1 (below) presents the relationship between the volume of a bead filter, feedrate, pounds of fish, and pond size for typical applications. The bead filter sizes indicated are the minimum recommended. Larger bead filters will not necessarily perform better, but will require less frequent backwashing and have a larger safety factor.
TABLE 1
The minimum size of a bead filter for a Koi pond is primarily controlled by the daily feedrate.
A properly sized UV light will assure control of algae blooms.
|
Bead Filter
Size (ft3)
|
UV Light
(
Watts)+
|
Flow
Range
(gpm)
|
Maximum Daily
Feedrate (lbs)
|
Amount of
Koi (lbs)*
|
Typical Pond
Volume (gal)
|
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1
|
25
|
5 - 15
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0.5
|
25 - 50
|
500 - 1000
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2
|
40
|
10 - 30
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1.0
|
50 - 100
|
1000-3000
|
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3
|
80
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15 - 45
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1.5
|
75 - 150
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1500-5000
|
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5
|
120
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25 - 75
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2.5
|
125 - 250
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2500-10000
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10
|
240
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50 - 150
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5.0
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250 - 500
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5000-20000
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+ Wattage requirements are approximate and will vary with quality of bulb and flow rates.
* Aeration backup systems are recommended to protect heavily loaded ponds from power interruptions.
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The bubble-washed bead filters are generally washed once or twice a week during the summer months in a typical koi pond application. They may be washed more often without adversely impacting nitrification performance. If the filters are not washed, they slowly clog, gradually shutting off the return flow to the pond. This decline in the return flow is usually visually evident, providing a convenient reminder for the need to backwash.
Bubble-washed bead filters perform better with frequent backwashing. Backwash frequencies of two to four times daily are used to carry heavy commercial loadings. Backwashing the filter once or twice a week is all that is required for most koi ponds. In the cooler winter months, backwashing frequency can be reduced to as little as once every two weeks.
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