Setting up an aquaponic system is not easy but not rocket science either. One of the many factors to consider is the size of the fish tank. Identifying the right size of the fish tank is very important as it determines how many fish you should rear in it, what type of fish you may rear in it, and the volume of water in the tank determines the size of the plant bed.
Choosing the right tank will help both your plants and fish to thrive and make your aquaponic system run smoothly.
Factors that Determine the Size of Aquaponics Fish Tank
The right size of the tanks will obviously depend on your purpose. You may want to set up a small system on your counter top. Some are more serious about producing food and need a larger tank and some may even look at aquaponics as a business venture.
Whatever your reason for going an aquaponic, there are two factors that you should keep in mind in determining the size of the fish tank:
Fish Type and Size
Fish are one of the main components in an aquaponic system. They provide food and fertilizer for the plants. There are many types of fish that can be used but not all fish can be used in aquaponics.
In choosing fish to rear, make sure to know the adult size of the fish. Some fish need space to thrive. A goldfish can thrive in a minuscule counter top aquarium where as catfish can grow up to 40-50 lbs so they need a large fish tank of at least 250 gallons. Koi also require large fish tanks to thrive while cods are only suitable on high-density tanks to suppress their territorial behavior.
Stocking Density
Aside from the type and size, the number of fish that you put in the system is also important. When determining the capacity of the fish tank, it is common to look at total fish length or weight rather than the number of fish. The idea is that bigger fish need more space. If you want to rear big fishes, you should choose a tank that can accommodate them.
For smaller-sized tanks with less than 50 gallons of water, the recommended stocking is 1 inch of fish for every 1 gallon of water. So, a 10-gallon tank can hold ten 1-inch fish or five 2-inch fish. For larger tanks that are over 50 gallons, the recommended stocking density is 1 lb of fish for every 5-10 gallons of water or 1-2 fish per 10 gallons of water.
Stocking more than 1 lb of fish for every 3 gallons of water is not encouraged as it may increase the possibility for fish stress, disease and overall imbalance in the aquaponic system.
One of the best fish to rear in aquaponics is tilapia. Most of its species thrive in the system. Most people start with a fish tank of at least 500 litres. This gives approximately 130 gallons which allow enough room for between 20 and 40 full grown tilapia.
Plant Bed
The volume of water in the fish tank determines the maximum size of your grow or plant bed. The aquaponics system works on the principle of the fish waste becoming food for the plants. The plants need the fish waste to thrive. On the other hand, they act as powerful filters and clean the water for the fish.
Buildup of fish waste in the water can be toxic for your fish. This is why adequate filtration is needed through growing more plant beds to recycle the amount of water in the tank. Fish tank to plant bed ratio should be applied. In general, the rule of thumb is 1 square foot of 12” plant bed needs 6 gallons of water.
Selecting the right fish tank
Growing fish in aquaponics is quite complex. Selecting fish tanks to the system will make your system right from the start. Here are some considerations in choosing fish tanks:
- Round fish tanks are recommended for aquaponics. Rectangular tanks allow solid waste to collect and rot in the corners.
- Tanks should ideally have a central drain in the tank’s bottom or a setup that allows solid waste to get out of the tank easily.
- Choose a fish tank that is sturdy, durable, non-toxic, food-safe and heavy-duty to withstand water pressure.
For more information read our articles on the benefits of aquaponics and the disadvantages of aquaponics.