By: Olav Austbø, Product Owner Feeding Solutions
Deep farming challenges the rules of feeding. When feed must be delivered to fish well below the surface, waterborne transport becomes a prerequisite. This naturally raises questions about pellet integrity and nutritional value as feed moves through different transport and introduction methods, and how this differs from airborne transport.
The need for consistent operator competence and a stronger knowledge foundation led AKVA group to focus on addressing these questions, forming the core objective of this project.
Feed is the largest cost in fish farming, and precision feeding determines performance. Accurate pellet introduction, controlled transport, and real-time adjustment enable better feed utilisation and proactive feeding decisions.
Waterborne feeding as a core enabler
Over the past five to six years, waterborne feeding has become a core enabler of deep farming, with increasing focus on the variables influencing feed quality.
Preserving feed quality from silo to fish is essential. Feed quality is not only defined by pellet shape, but also by nutritional composition, stability during transport, and how the feed is ultimately eaten and utilised.
Documenting performance under real farm conditions
To build documented insight, a joint research project was initiated with the Institute of Marine Research. The project was run under realistic operating conditions at Matre Research Station and partly funded by FORREGION Rogaland.
Three different feed transport and pellet introduction methods were temporarily installed and benchmarked under field conditions:
- airborne transport with doser-based pellet introduction
- waterborne transport with sluice-based pellet introduction
- waterborne transport with pellet introduction through pumps
For each method, pellet behaviour and energy consumption were quantified across varying transport lengths, transport velocities, and feed rates.
A benchmarking methodology tailored to real farm conditions was developed, combining standardised sampling, repeatable test setups, and independent laboratory analysis. Photo: AKVA group
Ragnar Nortvedt, Senior Research Scientist at the Institute of Marine Research (Havforskningsinstituttet) – PhD. Multivariate analyses, experimental design, evaluation of pellet texture and energy consumption data from the benchmarking trials. Photo: AKVA group
Key variables
Transport distance has been shown to be the main variable affecting pellet behaviour. Transport length should therefore be a key design criterion when planning a site. Deep farming or not.
Figure 1: Waterborne transport with sluice-based pellet introduction (method B) had lower fragment loss versus transport length than waterborne feeding with pellet introduction through a pump (method C). The airborne transport (method A) setup in this trial was without pipe bends, selectors or spreaders, which are known to generate fragment loss. Linear fit. Dosing rate =5kg/min, 9mm conventional feed, recommended transport velocity. Change in fragments measured from silo reference. Photo: AKVA group
In waterborne transport, water exposure causes gradual pellet softening and potential nutrient leaching, which must be considered during feed introduction.
Gentle pellet handling is critical. Once transport length is defined, velocity must be optimised to balance gentle handling with stable system performance and avoid clogging. This ensures predictable feeding and high uptime.
Figure 2: Increased velocity is a known variable for airborne feeding, and similar trends as for transport length are reflected in the different waterborne feeding transport methods. The only difference between the waterborne transport methods is the pellet introduction phase, Sluice vs Pump. Dosing rate =5kg/min, 9mm conventional feed, transport length =700m. Photo: AKVA group
Energy performance and system limits
Waterborne feeding demonstrated significantly lower energy consumption than airborne feeding over comparable distances. Microplastic generation from pipe wear is virtually eliminated, and noise levels are substantially reduced.
AKVA group is documenting a "once-through" pellet breakage test of waterborne transport method with pump pellet introduction, where pellets clearly have taken damage of both mechanical and hydraulic shear forces. Photo: AKVA group
The project has shown that AKVA group’s waterborne transport solution with water-sluice pellet introduction clearly outperforms both airborne feeding and today’s pump-based waterborne alternatives, which reach their limits much earlier due to rapidly increasing energy consumption and loss of pellet fragments.
From insight to application
The collaboration with the Institute of Marine Research has established a documented knowledge base defining key variables and performance limits.
Overall, the results indicate that waterborne feeding performance is primarily determined by early system-level design decisions and site-specific conditions, such as transport length and feed introduction method. The subsequent stage focuses on optimisation through available operational parameters, including transport velocity and feeding strategy 
itself.
With increased competence, AKVA group can assist operators achieving predictable feeding, high system uptime, and consistent performance within clearly defined operational boundaries.
Olav Austbø in AKVA group. Photo: AKVA group