Any system that involves growing plants without soil and supplied with nutrients through their water supply is considered a form of hydroponics. The plants still need something to root in, so soilless growing mediums for these systems may include:

• Expanded minerals like vermiculite and perlite.
• Pumice, gravel and crushed rock.
• Rice hulls, coco coir, sawdust and other byproducts of food processing.

There's no need to till, add amendments, measure the organic matter, fertilize or worry about compaction of soil when working with a hydroponics system. However, there is a need for a steady supply of water, and many modern hydroponics systems also rely on lighting and even heating in some climates. Growers also tend to purchase all the liquid nutrients needed for their plants, adding extra costs to production.

Hydroponics vs Aquaponics

The biggest difference between hydroponic and aquaponic systems is presence or lack of fish. Aquaponics systems rely on the fish for the majority or some of the nutrients required for the crops, resulting in lower recurring costs with each planting. The fish also provide a source of income. More testing and management is required in the aquaponics system, as a sudden change in temperature, water pH or nutrient levels could affect both the plants and fish. Hydroponics tend to be either manually or computer controlled to keep the release of nutrients as even as possible, so they're slightly less prone to certain fluctuations in water quality.

Yet hydroponic systems can still experience failures if sensors fail and irrigation gates stick open, so proper maintenance and care is required for both types of systems. Some hydroponics systems pack more crops into each square foot than corresponding aquaponics systems, but they also only tend to work with smaller plants like lettuce and radishes. With creative design and proper sizing, an aquaponics system can support even perennials like smaller tropical fruit trees and shrubs.