Biofilter Performance Standards
Tech Talk 106
"AES/B" stands for Absolute Efficiency Standard for Biofilters. AES/B Numbers indicate how many pounds of fish a biological filter can support in an exemplary recirculating system. They are only a quick reference for comparing our biological filters
. Note that as much as 50% additional ammonia conversion occurs on other wetted surfaces like tank walls and pipes but, since these nitrification surfaces are often eliminated by cleaning and chemical therapeutants, it is unwise to count on them (see "Biofilter Sizing" Tech Talk).
AES/B Numbers take into account the biofilm diffusion and oxygen availability characteristics specific to the biofilter type (bead filter vs rotating biological contactor, for example). Be aware that feed rate, feed protein content, pH, ammonia concentration, temperature, solids pre-filtration, and other variables have a pronounced effect on biofilter performance. Actual field performance can stray from the AES/B Number by a factor of 3 or more, based on these factors alone. Management skill, and even timing, are other variables, particularly for bead filters used for nitrification rather than solids removal.
AES/B Numbers hold for the following conditions only:
- Half-pound tilapia or catfish in indoor tanks.
- Nonsoil bottoms, low algae concentrations.
- Warm water (80°F, 27°C).
- Recirculation rate is at least one system volume per hour.
- 7.2 pH.
- 3 mg/l total ammonia-nitrogen (TAN) concentration.
- Two percent body weight per day feed rate, pelleted feed at 40 percent protein.
- Effective solids pre-filtration (except for bead filters).
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