How it helps an intensive eel RAS
Removes dissolved organic compounds (DOC)
Eels produce considerable mucus, fecal material, uneaten feed and other organic compounds.
A protein skimmer transfers hydrophobic organic compounds onto fine air bubbles and concentrates them into foam.
This reduces the organic load returning to the biofilter.
Reduces the load on the biofilter
By removing some organic material before it reaches the biological filter, the skimmer can help reduce the amount of oxygen and bacterial capacity required for decomposition.
The overall treatment concept becomes:
Eel tank → mechanical filter → protein skimmer → biofilter → degassing → oxygenation → eel tank
Improves water clarity
Fine-bubble skimming can remove colloidal and particulate-associated organic material that may otherwise make RAS water yellowish, turbid or "dirty-looking."
Helps control foam and surface-active compounds
Feed oils, proteins, mucus and other surfactants can accumulate in intensive systems. Skimming continuously extracts a portion of these materials rather than allowing them to circulate.
Reduces oxygen demand from dissolved organics
This is particularly important at high stocking densities. Less readily biodegradable organic matter in the water can mean less microbial oxygen consumption outside the intended biofilter.
Can improve biofilter stability
A cleaner influent to the biofilter can help maintain a more predictable nitrification environment. It does not replace the biofilter, which is still responsible for converting ammonia → nitrite → nitrate.
Potentially reduces off-flavor compounds
Some undesirable taste/odor compounds are associated with organic loading. A skimmer can help indirectly by reducing organic precursors, although geosmin and MIB are not reliably removed by conventional protein skimming alone.
