WATER TESTING & MAINTENANCE

Water Changer

Gravel-vacuum hose system that drains and refills without buckets.

Maintaining stage Water

Unplug before servicingHands out of the water firstDrip loop on every cableTest before you dose30 ppm CO₂ ceilingCycle before stocking

Water

Specification
Hose length	7–15 m
Tube diameter	12–19 mm
Connector	Universal tap adaptor
Vacuum head	Rigid, 25–40 cm
Temperature mixing	Yes on better models
Flow control	Inline valve

Technical parameters
Typical change	25–50% weekly
Drain rate	Slowed at substrate
Refill temperature	Within 1–2 °C of tank
Dechlorinator	Dosed for full tank volume
Max single change	50% — larger risks a swing
Sand safety	Hover, do not dig

A water changer is a length of wide hose with a rigid vacuum tube on one end and a tap connector on the other. Water is drawn out by the pressure difference at the tap, pulling debris off the substrate as it goes, and the same hose then refills the tank once the connector is switched over.

The point is not convenience for its own sake. A maintenance routine that requires carrying six buckets of water is a routine that gets skipped, and skipping water changes is the single most common cause of a tank going wrong. Making the change easy is a genuine improvement in animal welfare.

Two features are worth having: a temperature-mixing valve so the refill water matches tank temperature rather than arriving at tap-cold, and a flow control valve so the drain rate can be slowed at the substrate. Draining at full speed through a deep sand bed pulls the sand out with the water. Dechlorinator must go into the tank before or during the refill — never after.

Safety and welfare

Never drain more than 50% in one go. A larger change swings temperature, pH and hardness hard enough to kill livestock.
Dose dechlorinator for the full tank volume, not just the replacement volume, and add it before the new water goes in. Chlorine and chloramine kill filter bacteria on contact.
Match refill temperature to within 1–2 °C. A cold refill in winter is a reliable way to trigger ich.
Never leave the hose unattended while filling. An overflow of 100 litres onto a floor is a very expensive few minutes.

Using it well

Mark the target level on the tank glass with a piece of tape. It removes the guesswork about how much you have taken out.

Vacuum the substrate while draining, but hover over sand rather than pushing the tube into it.

Clean the filter media in the water you have just drained. It is tank-temperature and dechlorinated, which is exactly what the bacteria need.

Used with

Nitrate test kitCanister filter (media rinse)Sponge filter (foam rinse)Water Change Calculator

Note. Parameters are conventional ranges across the category, not the claim of any one manufacturer. Nothing on this page is for sale and no outcome for any plant or animal is guaranteed. Simulator output elsewhere on this site is a simplified model, not a measurement — confirm everything with a test kit and the equipment's own instructions.

Water Changer

Using it well

Used with

Works alongside