Recirculating Systems What you really need to know

What Is The Goal? To produce fish in a cost effective manner where the environment is controlled through water treatment and recirculation

Putting the Pieces Together Components Setup Operation Water Quality

Basic System Components Culture Tank(s) Solids Removal Biofilter Oxygenation Pump Temperature Control Fine & Dissolved Solids Removal Disinfecting

Types of Culture Tanks

Types of Tanks

Solids Removal Settleable solids Suspended solids solids that will generally settle out of the water within 1 hour under still conditions Suspended solids will not settle to the bottom of the fish culture tank Fine and dissolved solids < 30 micrometers

Settleable Solids Can be removed by: Well placed drains Sedimentation tank (clarifier) Mechanical filter (granular or screen) Swirl separator

Solids Removal Settling Tank

Settling Basin

Settling Basin Design Weir

Settling Basin and Biofilter Return

Suspended Solids Can Be Removed By: Screen Filtration Mechanical Filtration (sand or pelleted media)

Upflow Sand Filter

Bead Filters

Biofiltration Removes Metabolic Waste Products Ammonia Nitrite

Biological Filtration (Nitrification) Trickling Filters Bead Filter Rotating Bio-Contactor (RBC)

Trickle Filter Bioballs

Packed Tower Trickle Filter Trickle Filter Trickle Filter

Filter Media

Surface Area of Various Media

Bead Filter

RBC Rotating Bio-Contactor

Rotating Bio-Contactor RBC RBC

Oxygenation Aeration and Degassing Pure Oxygen Injection

In most cases, a system’s ability to add dissolved oxygen to water will become the first limiting factor in a system’s fish carrying capacity.

Regenerative Blower

Air Stones Fine Bubble Medium Bubble

Downflow Bubble Contactor

Related to feed input, number, size & species of fish Pump Pump selection is based on the amount of recirculation necessary to maintain good water quality. Related to feed input, number, size & species of fish

Temperature Manipulation Heater Chiller

Dissolved Solids Control Can Be Removed By: Foam Fractionator Water Changes Fine suspended solids increase the oxygen demand of the system and cause gill irritation. Dissolved organic solids (protein) can contribute significantly to the oxygen demand of the total system

Foam Fractionator (Protein Skimmer)

Break Time

The Set Up Things to think about

Putting it all together

Where to Start Inspect Parts Identify and Label Parts Read Directions Assemble System Without Glue Double Check 1-way Valves etc. Glue

Start-Up Break In Period Fill With Water Check For Leaks & Repair Let run for a few days and watch for new leaks Remove Chlorine

Biofilter Initiation Check Alkalinity Start adding SMALL amounts of household ammonia Bacteria should begin to colonize filter Run system for 2-3 weeks

Biofilter Initiation Option #2 Add 20-30 small to medium fish Use a reputable fingerling dealer Check fish for parasites and disease prior to adding them to the system Acclimate fish to receiving tank

Calculate Feed Feeding rates based on Fish Species Fish Size

Tilapia Stocking and Feeding

Calculating Feed Amount Example 100 fish weigh 10 pounds total Approximately 45 grams each According to chart use 3.2% of body wt. 10 lbs x 0.032 = .32 lbs or 145 grams Feed 145 grams splitting feed into several feedings

Recalculating Feed after 7 days Sample 25 fish and calculate total wt. 25 fish weigh 1314 grams 1314 grams / 25 fish = 52.6 g/fish 100 fish x 52.6 g = 5260g or 11.6 lbs New feed rate = 5260 g x 0.032 = 168g

Feed Conversion Ratio Growth = 1.6 lbs using 2.24 lbs of feed Now that you have a feed conversion ratio you can also calculate new feed rates based on this ratio

Calculating New Feed Rate Based on FCR 10 days feeding at the new rate 168g x 10 =1680 g 1680 g / 1.4 = 1200 g new growth New total weight = 1200 g + 5260 g = 6460 g New daily feed rate 6460 x .032 = 207 g Recalculate FCR regularly (1-2 months)

Water Quality After Feeding Watch ammonia levels Prepare water for partial change 2-3 55 gallon barrels Change 5-10% of water every 1-2 days Track feed, DO, Ammonia, Nitrite, pH and alkalinity Once system is stable add more fish

Adding More Fish Determine how many fish system can handle Look at capacity of biofilter based on surface area of media Continue to monitor and feed

Eat Fish