Aquaponic Fish Stocking Density

What is fish stocking density for an Aquaponic system?

In general, stocking density is the ratio of fish, based on their weight, to the unit or volume of water. When it comes to Aquaponics, it is a little, no, a lot more involved than that.

This is a highly debatable topic, as there is so many variables that determine the amount of fish you can/should stock into your system. Some of those things include: water flows, oxygen levels, pumping rates, the amount of plants in the system, the feed amounts, fish species, water temperature, water levels, etc.

For a well designed and balanced Aquaponic system, the ratio between plants and fish is dependent on your system size and how much the fish are fed.

 Commercial farms have large setups that not only include huge grow-beds to filter the water, but also expensive equipment such as bio filters, etc. These systems can thoroughly and automatically manage the water levels in the tank (especially ammonia and nitrates), keeping the water clean and allowing them to feed and stock more fish.
 However, for a backyard gardener that has a smaller system, the amount of fish and how much they are fed less is less in order to keep them healthy and to balance the system properly.

Disclaimer here: My research comes from experts, not those who are still experimenting with their systems and put out videos claiming to know all about Aquaponics and Aquaculture. Based on what they have to believe (and what we follow for our systems), the standard rule of thumb  is 1 lb. of (adult) fish for every 8-10 gallons of water. 

To calculate this, you need to know out the type of fish you want to stock and how big they will get before you either sell or harvest them. For tilapia, adult size is generally 1 lb; so you can keep 1 tilapia for every 8-10 gallons of water. In a 55 gallon fish tank, you can safely house 5-6 adult tilapia. Just don’t be tempted to buy 100 fingerlings as each of those cute little fish will grow up to be about a pound each, and depending on how heavy you feed them, within 1-2 years. To appropriately house that many tilapia, you will need about a 1,000 gallon  fish tank!

Once you have your fish in the system, you can experiment with feeding them (more or less) as long as you monitor the water conditions/levels and keep them where you want/need them to be. It is a lot easier to start out ‘small’ and experiment, growing a little at a time than it is to  stock heavier upfront and have multiple issues with your fish and your entire system.
Bottom line: Start with less fish than you think you need- you can always add more later. Carefully monitor your water levels and document them along with any water changes, number and amount of food provided daily, etc. This will help you grow your system and keep it balanced.
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I'm a gardener, posting related things as I find the time. There is a lot of great info I was keeping in folders; then realized there are others who might benefit from my research so I decided to share my findings online and get input from others.

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