Auqa Gadget 5 Gallon Hydrofill Reservoir – The easiest top off reservoir to refill is now here. Just slide out the easy to access acrylic drawer and fill it with up to 5 gallons of fresh water. Just put your favorite ATO pump in the reservoir through the included 4″ x 1″ opening in the back and you are ready to top off. Most of the time ATO reservoirs are made up of 5 gallon buckets, or trash cans that are very unsightly. Innovative Marine’s Hydrofill Reservoir removes the chance of spilling, using a slide out drawer as a funnel, letting you refill without having to move the reservoir.