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Current Culture H2O Glossary of Hydroponic Terms

Aeration: Diffusing air into and or through nutrient solutions using air pumps, water pumps and nutrient solution circulation. There is a very direct relationship between crop health and aeration levels in the root zone, reservoir and cistern. Aeration creates an “aerobic” environment where a lack of aeration creates “anaerobic” conditions ( favoring pathogens that are harmful to crops).

Aeroponics: A growing method often favored for plant propagation where bare rooted plants or cut stems supported by net pots or collars are intermittently or continuously misted or sprayed with nutrient solution in the root zone (rhizosphere). Aeroponics systems are best known for stimulating very rapid development in crops. Often considered to be an “advanced” growing method although present day technologies tend to be much friendlier than previous generations.

Add Back Kit: “Adding Back” to a nutrient solution refers to topping up a system or reservoir with additional nutrients or crop feeding components between nutrient change outs. For example, as the EC lowers due to crop nutrient uptake. The Add Back Kit allows nutrients, additives, descaling solutions and pH buffers to be added back to the solution gradually to avoid shock using water flow from the circulation pump. The fitting uses siphoning and is adjustable. When not in use to add feeding components, the valve can be used to add aeration to nutrient

Air Flow Regulator: A tool or device used to standardize and calibrate aeration rates. Allows growers to adjust a measurable amount of aeration for hydroponics systems, reservoirs or cisterns, with readings provided as Inches of Water. Additionally, an air flow regulator extends the service life of air and water pumps while reducing the potential for excessive aeration.

Air Pump Bank: An area or even entire room where multiple air pumps may be connected individually and/or in a series to provide healthy, pressurized air to supply manifolds and air stone for growth module or reservoir aeration. Air pump output may be controlled and measure by installing an Air Reg(s) to the system.

Air Stone: A porous and inert material constructed to receive pressurized air (air pump and manifold). When placed beneath the surface of water or nutrient solutions, the air is diffused into many small or micro bubbles that travel to the surface. For hydroponic use specialty air stones are preferred for the salinity and mildly acid nature of hydroponic nutrient solutions.

Boneless Under Current System: When an UnderCurrent system is supplied with the necessary Spin Tight fittings to plumb the modules supporting net pots or collars together while the installer supplies the piping cut to desired lengths for customized spacing in grow floor plans.

CCH2O Lid: The rigid and sturdy covering for a single growth module that supports net pot(s) for crops or as a covering for an Epicenter. CCH2O lids also feature access ports, so roots may be inspected without raising lids in order to see.

Chiller: Typically refers to a reservoir chiller. A reservoir chiller may be gas charged or uses heat exchangers to help keep hydroponic nutrient solutions at optimal temperatures in warmer growing environments. There are many different types and applications for reservoir chillers. Keeping reservoirs at optimal temperatures helps potentiate dissolved oxygen levels for roots while mitigating potential issues with root pathogens.

CIP (Clean In Place): Grow room management techniques and practices that allow thorough and effective sanitation and cleaning of growing equipment, systems, surfaces, etc without necessitating disassembly to save time. CIP practices help improve crop turn over times and save labor costs.

Cloning: In the plant world, this refers to the asexual propagation of plants, ie producing new plants without seed. Typically performed by cutting shoots from carefully selected plants in a healthy vegegtative stage of growth and placing the cut stems in a system and environment where they may develop roots. Cloned plants will share all the same genetic characteristics as the donor or Mother Plant, for example finishing at the same time and sharing the same harvest qualities from plant to plant.

Cloning Collars: Typically a circular disc of foam like material that can open and close for use in supporting cut plant stems to develop roots in cloning or propagation systems

Cold-water loop: Supply (cold) and Return (warm) water plumbing strategy for chilling multiple hydroponics systems with centralized chiller and heat exchangers.

Crop Cruising: Practiced primarily in RWC (Recirculating Water Culture) applications, “crop cruising” involves creating a stable, suitable condition for crop growth, with minimal emphasis on micromanaging conditional parameters. Typically with “crop cruising”, target parameter differential is wider ranging and less specific than “crop steering” applications. This broadened parameter requires less manipulation, allowing growing conditions to stabilize. Unlike “crop steering” which requires extensive micro management of irrigation practices, such as calculating dry backs, shot frequency and duration, run off EC, etc, “crop cruising” is relatively easy and much less thought intensive. Simply put, “crop steering” requires much less concern and intervention, making it well suited for today’s busy lifestyle.
Crop Steering = More worry, less time.
Crop Cruising = More time, less worry.

Crop Steering: Crop Steering is typically implemented in Drain To Waste, drip applications, involving the micro-management of irrigation cycles, sequencing intervals, dry back events, etc. The approach requires extensive instrumentation, automation and attention to detail. Though capable of producing strong results, the method is not user friendly and not well adapted to a broader cultivator base.

Cultured Solutions Nutrients: Crystal clear nutrients for high performance crops available as Dutch Style A&B base nutrients, Bud Booster additives, and a CocoCal supplement. UCRoots and ClearLine are root zone enhancers that reduce scale and biofilms. These complete and 100% soluble formulations are made to be the cleanest in the industry.

Deep Water Culture (DWC): A foundational hydroponic growing method still widely used and adapted. Bare plant roots grow into a depth of aerated nutrient solution. Little or no growing media is typically used and plants are often supported in the system with a net pot or neoprene collars. The UC Solo System is a popular example of DWC systems.

Delivery Manifold: A pipe or tubing assembly designed to deliver aerated nutrient solution to the Epicenter via a Return Pump following the Return Manifold

Descaling, Descaler Additives: Crop safe nutrient additives such as Cultured Solutions UC Roots or ClearLine that are effective in reducing nutrient salt accumulation and biofilms in irrigation lines, growing surfaces and root systems. Additionally these additives, when used as directed, will help maintain healthy ORP (oxidation reduction potential) values in reservoirs and hydroponic growing systems.

DO (Dissolved Oxygen):The majority of plants people cultivate prefer aerobic conditions in the root zone, ie they thrive in the presence of oxygen at the roots. Nutrient solutions with elevated DO (dissolved oxygen) levels stimulate faster growth rates and bigger yields. Increasing DO levels significantly (as in aeroponics and RDWC systems) reduces the need for higher fertilizer levels as plants absorb and use crop nutrients more efficiently. DO can be measured and controlled although the equipment is typically reserved for larger scale growers

Drain-Out Kit: A specialized kit or assembly supplied with piping and Drop-Tee’s that enables individual Under Current Growth Modules and Epicenters to empty completely during or between cropping from a single or multiple drain port(s) with or without the use a Drain-Out Pump.

Drain-Out Pump: A centrifugal style water pump or pumps plumbed to a Drain-Out Kit. With a drain-out pump, Under Current systems can be emptied to levels above grade, whether for drain to waste or reclamation purposes.

Drip irrigation, drip system: An irrigation or fertigation method using a series of tubing to deliver controlled amounts of moisture directly to planting sites. Drip irrigation systems can range from very simple to very complex, both from a design and operation perspective.

Drop-Tee: A specialty plumbing fitting that allows water to drop below the level of the connecting pipes by gravity or pump action. Ideal for Drain-Out systems, ensuring that no water pools may remain inside grow modules between nutrient change outs or crop turns.

EC (Electrical Conductivity): A measurement of the relative concentration of fertilizer dissolved into a crop nutrient solution. EC meters, monitors and testers discharge a mild electrical current into the nutrient solution, where the resistance encountered is proportionate to the level of nutrient ions dissolved into the solution being tested or monitored. EC is the most universal reading for determining fertilizer levels in a nutrient solution and is the base value where TDS and PPM measurements are derived from following a conversion, for example TDS 400 and TDS 700 scales

Epicenter: The “heart” of a recirculating deep water culture system (RDWC). Typically this is a UC module without a planting site where recirculating nutrient solution from the patented under current technology is continuously pumped back to before travelling through the system again. A float valve, monitors, dosers and other sensors may be installed at the EpicCenter

Feeding Schedule: A system for supplying crop nutrition at varying strengths and ratios in order to best meet the specific demands for each phase in a crop life cycle. Often scheduled as a weekly regimen for propagation, vegetitive growth, transitional development, early bloom, peak budding, ripening and flush. Professional level feeding schedules may also make distinctions for different types of growing methods or growth media types and environmental factors.

Fertigation, Fertigation System: The application of plant nutrients, fertilizers, additives or supplements to crops through an irrigation system. A fertigation system is similar in construction and operation to a variety of irrigation systems, ie pressure compensated drip systems, but is also designed to deliver applications of crop nutrients or nutrient solutions when watering crops.

Float Valve: A simple plumbing device typically installed in an EpiCenter or Reservoir that adds fresh water or nutrient solution from a supply as the nutrient solution becomes depleted from the system or reservoir. TIP: A float valve helps maintain more stable conditions in the root zone, for example pH or EC

Flush: An application of fresh water or a mild nutrient solution in a quantity and/or frequency that is intended to lower the concentration of nutrients or fertilizers in the rhizospehere, growing media or internally with crops.

Growth Module: A single or group of planting sites acting as a chamber for hydroponic roots in RDWC, DWC and aeroponics systems. Also referred to as a “mod”. For example, a particular Under Current system may have eighteen Pro Mods running off of two Remote Epicenters.

HPAC (High Pressure Aeroponics Cloning System): A high density aeroponics system used to stimulate explosive root growth in propagating plant cuttings. High pressure misters in the rooting chamber intermittently deliver an oxygen and nutrient rich mist to cut stems supported by cloning collars. HPAC systems are highly modular and are popular due to their accelerated rooting times and ability to reduce veg time by propagating larger and fuller cuttings. When used in conjunction with UnderCurrent RDWC systems, the use of growing media is greatly reduced or may be eliminated entirely.

Hydroponics: Growing plants without soil or simply “water culture”.


Joint: Interconnecting pipe between two growth modules.


Linear Air Pump: Air pumps that don’t use traditional diaphragm technology. Linear air pump designs are based on a piston like in a car engine. They are much quieter and more reliable than diaphragm pumps or blowers meant to put out the same amount of air. They can be installed in a series to increase or decrease air output requirements as needed, ie scalable.

Liquid fertilizer: A complete or partial spectrum of elements necessary for crop development supplied in a liquid formulation. Liquid formulations are preferred for ease of application and measurement. Additionally, the elements are often solubilized versus dry fertilizers making them easier to dissolve into water for use as hydroponic nutrient solutions. Dry fertilizers may introduce contaminants into the growing area during mixing  and handling, providing further benefit in use of liquid fertilizers.

Media Water Filtration: Typically one of the preliminary steps in RO (reverse osmosis) purification or may be used as a treatment for marginal water supplies where product water quality may not be as sensitive, ie dechlorination and sediment removal. The media in particulate filter(s) can be a blend or a combination of materials including zeolite..
NOTE: Commercial RO Membranes, Carbon Filters and Sediment Filters can be back washed for cleaning as part of regular maintenance to keep your RO system running at optimal for a longer filter working life

Mother Plant (Donor Plant): The parent plant kept or maintained for the purposes of supplying vegetative shoots for use as rooting cuttings, ie cloning or asexual plant propagation. Crops propagated from a mother plant will share all the same genetic traits as the original donor plant.

Multi-Mod Chamber: The base growth chamber module for either HPAC or Commercial UC system. Using interchangeable lids, the module can fit hundreds of clones, several larger plants or one singular extra large sized plant. The multi-mod chamber may be used for DWC, RDWC and aeroponics. The multi-mod chamber represents the highest level of flexibility in a robust hydroponic system design

Net Pot: A rigid mesh plastic pot designed to support a plant, for example in a CCH2O lid. The “open” design allows roots to grow into a depth of nutrient solution while maintaining adequate plant support and preventing light from entering the system.

Net Pot Insert: A purpose made or “tailored” disc fitting on top of a net pot to block out light and help reduce or negate the use of a growing medium.

Net Pot Insert Collar: A composite foam disc, smaller than the Net Pot Insert (above) that supports a plant stem while allowing for growth when used in conjunction with a Net Pot Insert. The foam collars may also be used to support plants in HPAC (high pressure aeroponic cloning) systems

Nutrient: An element(s) required for plant growth which may be supplied to the roots or through the leaves of crops. Nitrogen is an example of an element that is typically supplied through the roots while Carbon Dioxide is most commonly supplied through the leaves (as a gas).

Nutrient Change-Out: Emptying a hydroponic system, reservoir or stock tank during cropping to replenish with a fresh supply of nutrient solution. Nutrient change outs are typically performed weekly when following a crop Feeding Schedule.

ORP (Oxidation Reduction Potential): The potential of a disinfectant to inactivate microorganisms in bodies of water. It is a direct measure of disinfection power

Oxidizer: A substance that has the ability to oxidize other substances, for example in the purpose of neutralizing unwanted substances.

pH (potential hydrogen): In scientific terms this is the negative logarithm of hydrogen ions in solution, ie the more H+ ions in the solution, the lower the pH value. In practical terms this is the measure of acidity to alkalinity of a solution or substance from 0 to 14, with 0 being most acidic and 14 being most alkaline. Most hydroponic systems and growing medium types will operate best in a pH range of 5.5 to 6.5.
Optimal pH values help maximize nutrient absorption potential and healthy conditions in the root zone (rhizosphere)

PPM (Parts Per Million): A measure of the total concentration or specific elemental concentration of nutrient or fertilizer that is dissolved into a nutrient solution or as a measure of water quality


Recirculating Deep Water Culture (RDWC): The patented Under Current® recirculating deep water culture (RDWC) system features a proprietary method to circulate oxygenated nutrient solution throughout the root zone. This approach ensures pH and EC levels are uniform during the growing cycle, resulting in unmatched productivity, efficiency, and ease of use. Ideal for integration with automation and fertigation systems for commercial standardization.

Regenerative Blower: Used for regenerating oxygen levels in nutrient solutions via aeration (pressurized air delivery pipe with air stones in nutrient solutions), similar in work duty to a linear air pump. Regenerative blowers are designed for higher aeration delivery and efficiency levels. Ideal for larger scale applications. Regenerative blowers have a very long service life versus other types of air pumps.

Remote Epicenter: As Above, with “Epicenter”. The point of difference being that the Remote Epicenter may be installed at some distance from the UC RDWC system plant modules, for example outside the grow room or greenhouse. This allows for convenient or centralized access while not interrupting photoperiods to perform manual checks or to service the system.

Reservoir: A tank or barrel used to store and/or recirculate water or nutrient solutions. Note, cisterns may be another term used although more often for fresh water storage rather than nutrient solutions. Reservoirs and other materials coming into contact with hydroponic nutrient solutions should be chemically inert, ie they do not react with the slightly acidic and saline nature of nutrient solutions or pure water (RO filtered water) supplies.

Return Manifold: A pipe or tubing assembly designed to draw aerated nutrient solution through all of the growth modules in an UnderCurrent System back to the Epicenter via a Return Pump.

Return Pump: A continuously recirculating pump that keeps the flow of water, nutrients and oxygen circulating from the Epicentre through each of the growth modules in the UnderCurrent System.

Reverse Osmosis: A water purification method that removes virtually all impurities from water sources, yielding product water that contains “0” parts per million (PPM) or dissolved solids (TDS/EC)


TDS (Total Dissolved Solids): Total dissolved solids (TDS) is the term used to describe the inorganic salts and small amounts of organic matter present in solution in water.

UC Comm Mod: An Under Current growth module used in Commercial UC Systems of larger capacity (30 gallon) and footprint versus UC 8 gallon and UC XXL 13 gallon growth modules.

UC Module Cage: A heavy gauge galvanized wire support system for crops that is easily collapsible and stackable when not in use. A UC Module Cage helps maximize canopy management potential for healthier plants and bigger yield potential.

UC Parka: An insulative and reflective protective jacket that fits various Under Current System Growth Modules. UC Parkas can help reduce heating and cooling requirements while helping to buffer the root zone from external environmental changes.

UC SpinTight Bulkhead: A heavy duty large diameter plumbing connector that allows larger diameter rigid piping to connect to growth modules, epicenters or reservoirs. These fittings are an integral part of professional RDWC system construction and are also widely adopted for a variety of growing system construction or application types.

UC Solo System: A DWC (deep water culture) system offered by CurrentCultureH2O using a multi mod. These systems are highly expandable and adaptable. While ideal for smaller scale growers, larger scale growers use UC Solo Systems to help establish transplants for larger RDWC set ups.

Under Current System: The patented Under Current® recirculating deep water culture (RDWC) system features our proprietary method to circulate oxygenated nutrient solution throughout the root zone. This approach ensures pH and EC levels are uniform during the growing cycle, resulting in unmatched productivity, efficiency, and ease of use. Ideal for integration with automation and fertigation systems for
commercial standardization

VPD (Vapor Pressure Deficit): The amount of water vapor in the air surrounding the plant’s leaves plays a strong role in regulating the plant’s potential rate of photosynthetic activity–this is what VPD (vapor pressure deficit) is all about. When out of the sweet spot, crops suffer, and can easily be overworked to the point of stress or damage if humidity levels fall too low. Conversely, an overabundance of humidity will stifle growth rates, causing stretchy and weak growth that is prone to problems.