News

Page SEO Summary: This technical guide helps aquaculture professionals and procurement managers evaluate sinking fish feed pellet mills—covering technology, production processes, equipment selection, and investment considerations for sinking feed production.

Sinking fish feed remains the most widely used feed type in global aquaculture. For many farmed fish species—particularly bottom feeders and certain freshwater species—sinking pellets are the preferred or only suitable feed form. They are also the more economical choice for farmers, requiring simpler equipment and lower production costs than floating feed.

Sinking fish feed pellet mills are essentially standard pellet mills adapted for aquatic feed production. They use compression to form dense, water-stable pellets that sink rapidly to the bottom of ponds or tanks. While less technologically complex than floating feed extruders, sinking feed production still requires careful attention to formulation, grinding, and conditioning.

This guide provides a comprehensive technical framework for understanding, selecting, and procuring sinking fish feed pellet mills.

---

What Is a Sinking Fish Feed Pellet Mill?

Definition

A sinking fish feed pellet mill is a standard ring die or flat die pellet mill used to produce dense, water-stable feed pellets that sink when placed in water. The equipment uses compression (pressure) to form pellets from ground feed ingredients.

Operating Principle

Principle	Description
Compression	Feed ingredients are forced through die holes under high pressure
Binding	Natural binders (starch, protein) hold pellets together
Conditioning	Steam and moisture improve binding and durability
Cutting	The extruded pellet rope is cut to desired length

Key Characteristics of Sinking Pellets

Characteristic	Description
Density	High (sinks immediately in water)
Water stability	Moderate to high (15-60 minutes typical)
Starch gelatinization	Low (20-30%)
Pellet structure	Dense and hard
Production equipment	Standard pellet mill

---

Sinking vs. Floating Feed: Comparison

Key Differences

Aspect	Sinking Feed	Floating Feed
Production equipment	Standard pellet mill	Extruder/expander
Starch gelatinization	20-30%	80-90%
Pellet density	High	Low (porous)
Water behavior	Sinks immediately	Floats >30 minutes
Water stability	15-60 minutes	3-6+ hours
Production cost	Lower	Higher
Equipment cost	Lower	Higher
Feeding observation	Poor	Excellent

When to Use Sinking Feed

Scenario	Reason
Bottom-feeding fish	Fish naturally feed on bottom
Cost-sensitive operations	Lower feed cost
Small-scale farms	Lower investment
Certain species	Species-specific preference
Warm water ponds	Fast consumption reduces water stability need

---

Fish Species Suitable for Sinking Feed

Primary Species

Species	Sinking Feed Suitability	Notes
Catfish	Excellent	Natural bottom feeder
Carp	Excellent	Bottom feeder
Tilapia	Good (both)	Can use either
Trout	Good (both)	Often uses floating
Turbot	Excellent	Bottom feeder
Eel	Excellent	Bottom feeder
Lobster/crayfish	Excellent	Bottom feeder
Shrimp	Excellent	Bottom feeder

Feeding Behavior

Feeding Type	Species	Feed Form
Bottom feeders	Catfish, carp, shrimp	Sinking only
Mid-water feeders	Tilapia, trout	Either
Surface feeders	Some species	Floating preferred

---

Sinking Feed Production Process

Complete Process Flow

Stage	Equipment	Purpose
Grinding	Hammer mill	Reduce raw materials to uniform particle size (0.5-1.5 mm)
Mixing	Mixer	Blend ingredients uniformly
Conditioning	Conditioner	Add steam and moisture; soften ingredients
Pelletizing	Pellet mill	Form dense pellets
Cooling	Cooler	Reduce temperature and moisture
Screening	Fines screen	Remove fines
Packaging	Bagging system	Final product packaging

Key Process Parameters

Parameter	Typical Range	Importance
Grinding fineness	0.5-1.5 mm	Pellet quality and durability
Conditioning temperature	70-90°C	Starch gelatinization; binding
Conditioning moisture	15-18%	Pellet density and durability
Die compression ratio (L/D)	1:10 to 1:14	Pellet density and water stability
Pellet mill temperature	80-95°C	Material binding
Pellet moisture (final)	10-12%	Storage stability

---

Pellet Mill Specifications for Sinking Fish Feed

Key Specifications

Specification	Recommendation	Rationale
Motor power	Depends on capacity	Match to production target
Die diameter	350-600 mm	Capacity-dependent
Die compression ratio (L/D)	1:10 to 1:14	Good water stability
Die material	Premium alloy (X46Cr13 or higher)	Durability; wear resistance
Conditioner	Recommended	Improves binding and durability
Feeder	Variable speed	Controlled feed rate

Capacity Options

Capacity (kg/h)	Motor Power	Die Size	Application
50-100	7.5-15 kW	250-300 mm	Small farms
100-300	15-22 kW	300-350 mm	Small feed mills
300-500	22-37 kW	350-400 mm	Commercial mills
500-1,000	37-55 kW	400-500 mm	Large feed plants
1,000-2,000	55-75 kW	500-600 mm	Industrial operations

---

Raw Materials for Sinking Fish Feed

Common Ingredients

Ingredient	Function	Typical Inclusion
Fish meal	Protein source	15-35%
Soybean meal	Protein source	20-40%
Corn/rice bran	Carbohydrate source	15-30%
Oil	Energy source	3-8%
Vitamins/minerals	Nutritional balance	1-3%
Binders	Water stability	2-5%

Key Ingredient Requirements

Requirement	Why
Fine grinding	Better pellet quality and fish digestion
Consistent moisture	Reliable pelletizing
Proper protein/fat balance	Nutritional requirements
Binders (starch, gluten)	Water stability

---

Water Stability: Critical Quality Parameter

Why Water Stability Matters

Reason	Impact
Prevents feed waste	Pellets disintegrate before fish eat
Reduces water pollution	Prevents nutrient loading
Improves FCR	More feed consumed; less wasted
Maintains water quality	Less organic matter in water

Achieving Good Water Stability

Factor	How It Helps
Fine grinding	Better binding
Good conditioning	Starch gelatinization
Proper die compression	Denser pellets
Binders	Improved cohesion
Cooling	Sets pellet structure

Water Stability Test

Test	Method	Target
Static water test	Place pellets in water; observe disintegration	Minimum 15-30 minutes
Agitation test	Gently stir in water	Minimum 30-60 minutes

---

Investment Considerations

Equipment Cost Estimates

Capacity (kg/h)	Pellet Mill Cost (USD)	Complete Line Cost (USD)
50-100	$3,000-8,000	$10,000-25,000
100-300	$8,000-20,000	$25,000-50,000
300-500	$20,000-35,000	$50,000-100,000
500-1,000	$35,000-60,000	$100,000-200,000
1,000-2,000	$60,000-100,000	$200,000-400,000

Additional Costs

Cost Category	Estimated
Installation	5-15% of equipment cost
Commissioning	$1,000-5,000
Shipping	Destination-dependent
Training	$500-3,000
Spare parts	10-20% of equipment cost

---

Quality Control

Key Quality Parameters

Parameter	Target	Why It Matters
Water stability	>15-30 minutes	Prevents waste
Durability (PDI)	>95%	Handling and transport
Moisture	10-12%	Storage stability
Diameter	±0.5 mm	Species-specific
Length	2-3× diameter	Feeding behavior
Color	Consistent	Quality indicator

Quality Testing

Test	Equipment	Frequency
Water stability	Beaker; timer	Every batch
Durability	PDI tester	Every batch
Moisture	Moisture analyzer	Every batch
Size	Calipers; gauge	Every batch

---

Procurement Checklist: Sinking Fish Feed Mill

Production Requirements

• □ Target capacity (kg/h) defined
• □ Species to be fed identified
• □ Pellet size and water stability requirements confirmed
• □ Raw materials available

Equipment Specifications

• □ Pellet mill type selected (ring die preferred)
• □ Motor power confirmed
• □ Voltage/frequency match site supply
• □ Die compression ratio: 1:10 to 1:14
• □ Conditioner included
• □ Cooling system included

Complete Line

• □ Grinding equipment included
• □ Mixing equipment included
• □ Conditioning system included
• □ Cooling and screening included
• □ Packaging equipment (if needed)

Commercial

• □ Equipment investment budgeted
• □ Complete line investment estimated
• □ Operating cost projected
• □ Raw material cost calculated
• □ Payback period estimated

Supplier Evaluation

• □ Supplier experience with sinking feed
• □ References from aquaculture projects
• □ Spare parts availability
• □ Warranty and support terms

---

Frequently Asked Questions

1. What is a sinking fish feed pellet mill?

A sinking fish feed pellet mill is a standard ring die or flat die pellet mill used to produce dense, water-stable feed pellets that sink in water. It uses compression to form pellets from ground feed ingredients.

2. How is sinking feed different from floating feed?

Sinking feed is produced by compression (standard pellet mill) with low starch gelatinization (20-30%). Floating feed is produced by extrusion/expansion with high gelatinization (80-90%). Sinking feed is denser, less expensive to produce, and suitable for bottom-feeding fish.

3. What fish species eat sinking feed?

Catfish, carp, shrimp, lobster, eel, turbot, and other bottom-feeding species prefer sinking feed. Tilapia and trout can eat either, depending on preference and farming practice.

4. What capacity do I need?

Match capacity to your farm size or market. Small farms: 50-300 kg/h. Commercial operations: 300-1,000+ kg/h.

5. How much does a sinking feed pellet mill cost?

A pellet mill costs $3,000-100,000 depending on capacity. A complete line costs $10,000-400,000+.

6. What raw materials are needed?

Common ingredients: fish meal, soybean meal, corn/rice bran, oil, vitamins/minerals, and binders. Formulation depends on the target species.

7. What is water stability and why is it important?

Water stability is how long pellets stay intact in water (15-60 minutes typical). It prevents feed waste, reduces water pollution, and improves feed conversion.

8. Is sinking feed production profitable?

Yes. Sinking feed is the most common and economical form of aquafeed. With growing aquaculture demand, sinking feed production offers good returns with lower investment than floating feed.

---

About the Author

Zhang Wei – Senior International Sales Engineer, Shandong Changsheng Machinery Co., Ltd.

Zhang Wei has over 12 years of experience in the biomass and feed pellet mill industry, with a background in mechanical engineering and international project execution. He has managed feed production projects for aquaculture, livestock, and poultry operations across Southeast Asia, the Middle East, Africa, and Latin America.

With hands-on experience in both the manufacturing workshop and client-side operations, Zhang brings practical insights into successful equipment procurement—from the factory floor to the customer’s feed production facility.