Water Heating

Maintaining the correct reservoir temperature is one of the most important — and most commonly neglected — aspects of hydroponic growing. Water heating equipment keeps your nutrient solution within the 18–22°C optimal range for root health and dissolved oxygen, particularly during cold UK winters when unheated grow rooms can drop your reservoir temperature to levels that significantly impair plant metabolism and root function.
Why Reservoir Temperature Matters
Root enzyme activity, nutrient absorption and dissolved oxygen are all directly affected by solution temperature. At temperatures below 16°C, root cell metabolism slows significantly — nutrient uptake reduces, root development slows and plants visibly stall. Below 12°C, root growth effectively stops and the risk of Pythium (root rot) pathogens increases, as the plant’s immune response is reduced at low temperatures. In a UK winter grow room, an unheated reservoir in a cold loft or outbuilding can easily drop below these critical thresholds overnight.
At the other extreme, temperatures above 24°C rapidly deplete dissolved oxygen — increasing the risk of anaerobic root conditions and Pythium colonisation that causes the characteristic brown, slimy roots associated with root rot. The 18–22°C range balances maximum dissolved oxygen with optimal enzyme activity for vigorous, healthy root development.
Aquarium and Inline Heaters
Submersible aquarium heaters are the most popular solution for reservoirs up to 100L — simply submerse the thermostatically controlled heater in your reservoir and set the target temperature. For larger reservoirs and inline systems, inline water heaters fit directly into the irrigation pipework, heating water as it flows past a heating element. Always use a dedicated aquarium-rated thermometer to verify actual reservoir temperature rather than relying solely on the heater’s built-in thermostat.
We have been supplying water heating solutions to UK hydroponic growers since 2017. Browse the full range below.