Collection: ATO Systems

An auto top-off replaces the fresh water an aquarium loses to evaporation, which is what stops salinity climbing between water changes. The complete systems here pair a level sensor and a small controller with either a DC pump or a solenoid valve fed from a reverse osmosis line, and most add a second sensor or a mechanical float valve as protection against overfilling. Liquid level sensors for controller-based setups and automatic water changers are listed alongside them. Reservoirs are sold separately, so check what a kit includes before ordering.

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What an auto top-off does

Water evaporates from an aquarium; the dissolved salt does not. Left alone the level drops and salinity rises, then falls again sharply when the tank is topped up by hand. An auto top-off adds fresh water as it is lost, so specific gravity stays where it was set instead of cycling. It is usually the first piece of automation added to a marine tank.

How the systems here differ

Sensing - optical sensors are the most common, often paired with a second sensor or a float valve as backup.
Delivery - most kits include a small DC pump; solenoid versions instead open a valve plumbed to a reverse osmosis line.
Standalone or controller-linked - some units run on their own, others connect to an aquarium controller for logging and alerts.
Sumpless designs - kits built around a hang-on box for aquariums without a sump.
Liquid level sensors - sold individually in several lengths for reading depth in a sump or reservoir.
Automatic water changers - units that remove old water and add new on a set interval.

Installing one safely

An auto top-off fails in one direction that matters: it carries on adding water. Mount the sensor away from bubble streams and surface movement, keep the outlet above the water line or fit a siphon break, and fill the reservoir with fresh water only, never saltwater. Size that reservoir to your evaporation rate so refills land on a comfortable interval rather than daily. Where a backup float valve is supplied, fit it rather than leaving it in the box. Email sales@jlaquatics.com to match a system to your tank.

J&L Aquatics was formed in December 1997

Our business was started from our love of the aquarium hobby. We at J&L Aquatics felt that the Canadian aquarist should have the option to purchase top quality supplies, equipment and livestock other than the generally over priced local retail stores.

Collection: ATO Systems

Additives

Controllers & Testing

Pumps & Plumbing

Aquariums & Sumps

CO2 Equipment

Clearance & Open Box

Decorations

Lighting

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What an auto top-off does

How the systems here differ

Installing one safely

J&L Aquatics was formed in December 1997

604-444-1161

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