Where do the nutrients come from in the aquaponics solution?

Answer 1

Nutrients for the plants come from excrement, mostly urine, from the fish.

In an aquatic environment, urine is broken down quickly to ammonia by bacteria.

The ammonia is toxic and will kill the fish unless it is converted to nitrites by other bacteria, which is a reason getting a new fish tank "cycling" is very important.

A third group of bacteria converts the nitrites to nitrates, and the nitrates are used as a nutrient by plants.

The plants absorb the nitrates, and the water is returned to the fish, good as new.

Solid waste from the fish is usually removed by settling it out at some point in the system. It is valuable, as it contains more nutrients, which will support yet other groups of bacteria, and these can be food for various creatures that fish can eat. Alternately, it can be used to fertilize plants.

The nature of the system depends to a degree on what the fish are eating. Many fish eat algae that grows in the system, or tiny animals that feed on the algae. Most people pursuing aquaponics feed their fish with food they buy or grow. Many fish like lettuce, especially if it is wilted. Many fish like duckweed, which grows at an amazing speed. There are a host of types of fish food, ranging from natural, such as frozen or dried shrimp or bloodworms, to things that do not sound like fish food at all, such as corn or soybeans. Since fish excrement comes from what the fish are eating, and the excrement is nutrition for the plants, it bears paying attention to what the fish are eating.