The water stability of fish feed pellets refers to the performance of keeping constituents from dissolution and diffusion after fish feed soaking in water for a fish-feed-pellet1certain period of time. In general, stability is indicated with the ratio of fish feed diffusion amount and quality in water per unit time, or with the minimum time without diffusion for fish feed in water, which always requires the diffusion rate of fish feed less than 20% (soaking for 30 minutes).

As the world feed industry develops continually, the requirements for various indexes of pellet feed have become higher and higher, not only requiring good inner quality (like nutritional property, disease prevention, and industry environmental protection, etc.) but also requiring high external quality (like color and taste of pellets, size, diffusion rate and so on). The particularity of the living environment requires formula feed with great stability in water, avoiding fast scatter, dissolution, and loss, so stability is an important index for quality assurance. Showing influence factors of fish feed pellet water stability as follows:

  • Mash particle size

The particle size of fish feed has a significant effect on the stability. On the one hand, if the fineness of pulverization is large, it is easy for water to aquatic-feedpermeate pellet feed and cause scattering; on the other hand, grinding particle size also has a definite influence on process flow, such as mixture and tempering steam, etc. While small particle size can make raw materials sufficient and even mixing, in favor of material tempering, stimulating natural binder component for better bonding effect, and meanwhile, the swelling property of the material is close to accordance, all of which assist in obtaining better stability in water. As a raw material, granularity determines the surface area of feed composition, the thinner particle size, the larger surface area, and the stronger ability to absorb the moisture in the steam before granulation, which can prolong the dwell time in the fish body, promote the absorption effect and reduce water pollution. In general, after grinding, fish feed raw material should pass a 40 mesh standard sieve and less than 20% oversized product for a 60 mesh standard sieve, while prawn feed raw material should pass the 60 mesh standard sieve.

Basic Requirements for Material Grinding Particle Size of Aquatic Feed

  • Tempering during feed processing

By adding steam to soften materials with more plasticity, the materials are easy for extrusion forming, thereby enhancing the granulating function of fish feed pellet extruder. Moreover, water stream heat can make starch of bait full gelatinization, make protein denaturation, and help starch turn into soluble carbohydrates so as to improve the digestive utilization ratio. Moreover, the improvement of granule density brings a bright and clean appearance that is uneasy to be eroded, increasing stability in water. Additionally, high-temperature function during the tempering process can kill harmful germs like colibacillus, salmonella, and so on, raising the storage properties of products and beneficial to fish health.

  • Binding agent

Binding agents, the peculiar additive with the bonding and molding function for fish feed, can be broadly separated into two categories: natural substances and chemical synthesis substances. The former can be divided into saccharides (starch, wheat, corn flour, and the like) and animal gels (bone glue, hide glue, surimi, and so on) according to the ingredient, while the latter can be divided into carboxymethylcellulose and sodium polyacrylate, etc. In the process of fish feed production, a moderate binding agent can advance the stability of feed in water.

Solutions for Improving Fish Feed Water Stability

In allusion to a variety of factors influencing fish feed pellet water stability, FANWAY Fish Feed Machinery, an expert in manufacturing various fish feed machines with high quality and stable performance, provides the following countermeasures:

Choosing suitable feed raw materials

Some raw materials can increase the stability of fish feed in the water, so the larger the proportion they are in the feed formula, the better stability the feed will have, otherwise, the stability in water will be worse. When designing the formula, fish feed producers should follow the below principles: floating-fish-feed-extruderFirst, for those same types of raw materials, try to choose the one with stronger stability, for example, choose flour among flour, corn, and rice bran, choose cottonseed meal among cottonseed meal and rapeseed meal, and choose fish meal among fish meal and silkworm chrysalis. Second, for the same raw material, its water tolerance and freshness are also different, choose the one with stronger water resistance and better freshness. Third, try to choose raw materials with animal protein under the circumstance of cost permitting because animal protein has better granulating efficiency than plant protein.

Appropriate starch and crude fiber

Under high temperatures and high moisture conditions, starch is easy to past-forming, becoming one of the important raw materials influencing fish feed stability in water. Because the requirement for fish feed protein level is higher, there are some limitations for the dosage of starch-type materials and the appending proportion should not be too big. During the production process, adding moderate flour can be conducive to improving pellet feed stability in water, but due to the higher cost of superior flour, it’s common to add 13%-15% wheat shorts in the actual production. The crude fiber content in fish feed should be controlled within 3%-5% so as to enhance water tolerance, but the crude fiber content in herbivore fish mixed feed could be duly higher, specifically, feed for fingerling should be controlled within 8 percents and feed for adult fish should be controlled within 12 percents.

Proper use of binding agent

Currently, there are many kinds of adhesives with different effects. When choosing a binding agent, please note the following points:

  • Considering the feeding habits of fish and the requirements of bait stability in water, usually, fishes with slower ingestion need higher stability while fishes with faster ingestion need lower stability.
  • Considering the property, suitable quantity, and cost of the binding agent.
  • Considering the interaction effect between adhesive and feed to see if nutrient content would be broken.
  • Considering the nutritive value of the binding agent and its influence on fish growth and livability.

Practice indicates that the binding agent of agricultural and sideline products (like wheat gluten, rice gluten, α – starch and wheat shorts, etc.) have good cohesiveness that can produce good stability in water; attapulgite and bentonite also have better cohesiveness and a certain amount of mineral element, suitable for low price feed with low stability in water.

Fitting fineness of pulverization


The product granularity largely depends on whether the grinding equipment is fitting or not, so choosing a suitable fish feed mill is crucial if feed producers want raw materials to achieve perfect fineness. In order to avoid bad particle size caused by improper grinding equipment, we have launched a 9FQ series fish feed hammer mill with high performance in grinding production, power consumption, and pulverization process, which makes particle size more guaranteed.

Controlling the tempering well

Lots of feed plants use steaming for tempering, that is, directly putting steaming into ready-prepared materials for hydro-thermal treatment. Therefore, it is of vital importance to control the speed of the feeding well and choose the time, temperature, pressure, and water content of the tempering well.

Regulating cooling of fish feed well

Most often, feed producers use fish feed cooler machines for cooling, and the temperature of the pellet just discharged from the cooler is 6-9 degrees Celsius higher than indoor temperature and the water content after cooling is 12%-12.5%. In the process, cooling time and air amount should be chosen depending on materials, pellet feature, and fish feed cooler types, but in general, pellet temperature after cooling should never go above 3-5 degrees Celsius than the indoor temperature.