XP Aqua Sumpless ATO2

Auto top-off built for tanks without a sump. The XP Aqua Sumpless ATO 2 is the first auto top-off designed specifically for aquariums with no sump. It pairs the same reliable dual-optical sensor and DC pump as the Duetto with a Flexi Overflow Box that mounts on the glass, so AIO and nano keepers get hands-off, precise top-off without drilling or a sump. Have a sump or open rim instead? See the Duetto2 ATO.

Key Features

• The first and only ATO built for sumpless AIO and nano aquariums
• Dual-optical sensor: a primary level sensor plus a secondary backup for overfill protection
• Includes a Flexi Overflow Box with a magnetic mount for glass up to 1/2 inch
• Complete kit with a quiet 74 gph DC pump, tubing, and power adapter
• Precise, plug-and-play water level control with no programming needed
• Works on both freshwater and saltwater aquariums

Specifications

Setup

• Mount the Flexi Overflow Box on the tank rim with the magnetic bracket
• Set the sensor to your target level and place the pump in your RO/DI reservoir
• Plug it in; it tops off automatically and the backup sensor prevents overfilling
• Use RO/DI or fresh top-off water only, never saltwater

Pair It With

• XP Aqua Duetto2 ATO for tanks with a sump or open rim
• AutoAqua Smart ATO Nano G2 for a simpler single-sensor option
• AutoAqua Inline TDS Meter to monitor your RO/DI water quality
• Browse more water care

Frequently Asked Questions

Why is it called sumpless?
It is built for AIO and nano tanks that have no sump or overflow. The included Flexi Overflow Box does the job of an overflow so the system can top off cleanly.

Freshwater or saltwater?
Both. It keeps the water level and salinity steady on any tank, and is especially handy on nano reefs.

Do I use fresh or salt water in the reservoir?
Fresh RO/DI water only. Evaporation leaves salt behind, so topping off with saltwater would raise your salinity over time.

How is it different from the Duetto2?
The Sumpless ATO2 adds the Flexi Overflow Box for tanks without a sump. The Duetto2 mounts its sensor directly and suits tanks that already have a sump or open access.