The Well 5 Gallon ATO Reservoir — Acrylic with Lid for Stands - Reef Casa

The Well is the freshwater reservoir that feeds your auto top off system. Five gallons of custom made acrylic, lid included, built to slide inside Reef Casa stands.

Our advice: this is the half people forget to buy

An ATO without a reservoir is a pump with nothing to pump. People buy the system, hook it to whatever plastic bucket is lying around, then wonder why it looks like a job site under the tank.

And remember: an ATO doesn't get installed the night before you leave. You need to have watched it run while you were home. That goes for the reservoir too — you want to know how long 5 gallons lasts in your room before you go away for a week.

Because the real job of an ATO isn't vacations. It's holding your salinity and temperature steady every single day, and keeping your pump from running dry. You cannot top off once a week and expect a stable environment. Stability is the key to corals that don't merely survive — corals that grow, and hand you colours worth looking at.

What the manufacturer states

• Custom made acrylic
• Ships with its own custom made lid
• Designed specifically to fit inside Reef Casa stands
• Holds 5 gallons of fresh water

Dimensions

• Width: 6.5 in (165 mm)
• Length: 13.38 in (340 mm)
• Height: 12.92 in (330 mm)

It's a narrow, tall footprint rather than a square tub — that's what lets it tuck into a stand without eating all the room under your tank.

What's included

• 1 x 5 gallon ATO reservoir
• 1 x custom made lid

The lid isn't a detail: an open reservoir under a cabinet collects dust, and that dust ends up in your tank.

What goes with it

• Level-O Auto Top Off — the system that pumps water from The Well into your tank. Dual laser optical sensors, 74 gph DC pump. Sold separately.
• Reef Casa Nano Cabinet — the stand The Well was sized for.
• Reef Casa Cube 15 — 15 gallon all-in-one nano reef.

Why buy it at ReefSolution

We are an authorized Reef Casa dealer. Secure shipping anywhere in Canada. Free shipping available depending on your order total.

Frequently asked questions

Does The Well come with an ATO system?

No. The box holds the 5 gallon reservoir and its lid. The top off system — pump, sensors, controller — sells separately. Reef Casa's Level-O is built to pair with it.

Will it fit my stand?

Reef Casa sized it for its own stands. Its dimensions are 6.5 in wide x 13.38 in long x 12.92 in tall (165 x 340 x 330 mm) — measure the clearance under your tank if you run a different cabinet.

Do I put saltwater in it?

No. A top off reservoir holds fresh water. It replaces what evaporates from your tank — and salt doesn't evaporate, it stays behind. Putting saltwater in would drive your salinity up without end.