Using the following principles when building your hydroponic system will effectively aid in growing good cannabis.

Design Principles: The following problems must be solved to build an efficient and functioning hydroponic system. The first five principles deal with your plants roots and their health.

1. Nutrient solution flow-rates in the root zone must be adequate. Circulation ensures the roots will receive adequate dissolved oxygen and nutrients. Usually 2 litres per minute per root-zone/gully for optimum results in nft (1/2 gal/min). Circulation also ensures that opportunistic fungi that thrive in stagnant water will not gain foothold. With nft, a slope of 1/30 - 1/50 will ensure that nutrients flow steadily past the root zone.
2. Optimum nutrient solution temperatures for maximum dissolved oxygen. Remember, water holds less oxygen at higher temperatures. Optimum temperature would be 20-24 C degrees, 68-75 F degrees. Solution at 20 C / 68 F holds about 9 ppm oxygen at 100% saturation, when the solution is 30 C or 86 F it holds 7.5 ppm oxygen when fully saturated (100%, at sea level). It is assumed at this point that solution temperature will equal root-zone temperature.
3. Nutrient solution must be aerated vigorously for maximizing dissolved oxygen levels. Dissolved Oxygen levels should be a minimum of 4 mg/l up to 10 mg/l or more (super-saturation). Dissolved Oxygen is required for root respiration and health. High DO-levels will result in faster root initiation and growth.
4. Raised drain in the root zone for small solution reserve in case of pump failure. Especially useful if no medium or very little medium is used in the system.
5. Non-toxic materials for all parts of the system. Food grade PE-plastic, PE-HD, PET, PEX and PP plastics are materials known to be safe for use in hydroponics. Non-toxicity ensures that no nutrient-lockups or accumulation of harmful substances will occur - both the plants and growers safety.

The following section deals with the practical every-day ergonomics of a hydroponics system.

6. System must be failure safe in case of situations like pump failure, flooding of the channels or clogging of the drains. A Secure system is an absolute requirement. Simplicity will lead to fail-safe designs more often than not. Usually this problem/principle is really easy to solve. Nutrient solution leakage may cause plant death, material damage or other serious problems including risk of electrocution. Clogging pipes and drains and siphoning of the solution are the most popular problems (authors experience) stemming from the sub-standard design and testing.
7. Any part of the system must be easy to assemble, access, maintain, clean and disassemble. Careful planning will make jobs like nutrient solution change or removal of plants easy. This principle points to - simplify, simplify, simplify! Remove any part that is not absolutely necessary and then optimize the remaining parts.
8. Support for plants or trellising netting must be readily in the system or easy to incorporate into the system. Failing to provide adequate support will normally produce damaged plants during blooming.
9. The root zone and nutrient solution should be protected from any light. Algae will start growing in the solution if it is not protected from light. Feeding lines and growing mediums clog easily, along with slimy layers of protozoa covering the waterline as a result of algae. It is also noted in some sources that light deters root growth.

Finally, this applies to any system, hydroponic or not.

10. The system should be sustainable, Efficiency. Reusability. Durability. Recyclability. In other words, as little materials and energy should be needed for construction and maintenance of the system. It should be durable as a result of the materials and energy expended, and finally, after its lifecycle is over it should be easy to use elsewhere or recycle.