The Hydor Automatic Feeder is an automatic fish feeding device that attaches to the top of your aquarium and dispenses dry food at scheduled intervals while you're away. Hydor made a popular model called the Hydor Automatic Feeder AT1 for many years. It uses a rotating drum mechanism and a timer to drop preset food portions into the tank up to four times per day. If you're traveling for a few days or simply want consistent feeding times without being home, it handles the job reliably once calibrated correctly.
This guide covers how the Hydor AT1 works, how to set it up correctly, how it compares to competing models, and the common mistakes that cause overfeeding or missed feedings.
The Hydor AT1: Overview and Specs
The Hydor AT1 is a drum-style automatic feeder. It uses a cylindrical food chamber with an adjustable opening that rotates to drop food into the tank on a timer. The timer is set by rotating a dial with pegs that engage a trigger mechanism. You insert white pegs at the intervals you want feeding to occur.
Specifications for the AT1: - Food capacity: approximately 100 mL - Feeding frequency: up to 4 times per day - Compatible food types: dry pellets, flakes, granules (not freeze-dried or gel food) - Power: 2 AA batteries - Mounting: clips to aquarium rim or glass edge up to about 3/4 inch thick
The AT1 is no longer in current production by Hydor, but it remains widely available as new-old-stock and used units. Replacement parts are limited. If you're considering the AT1, it's worth buying a backup unit while they're still available, or looking at current-production alternatives that offer more features.
Setting Up the Hydor Feeder
Mounting Position
Mount the feeder at the tank edge closest to the aquarium's filter intake or an area with moderate water surface movement. This ensures that food dispensed drops into a area where it moves around and reaches the fish rather than collecting in one corner and rotting.
For tanks with a glass canopy, you'll need to leave a gap of at least 2-3 inches for the food to fall through. Some canopies have a pre-cut feeding hole; use that if available. The feeder should be positioned so the drum opening is directly above open water, not above the tank rim or frame.
Avoid mounting directly above a heater or powerhead. The vibration from powerheads can cause the drum to rotate unexpectedly, and heat from a heater affects the timer mechanism accuracy.
Loading the Food Chamber
Fill the drum chamber to about 2/3 full. Overfilling causes jamming where food compresses in the opening and blocks the dispenser. The drum opening size is adjustable by rotating the drum collar: a smaller opening drops fewer pellets per rotation, a larger opening drops more.
Start with a smaller opening setting and run a test feeding by pressing the manual feed button. Count the pellets that fall and compare to what you'd normally hand-feed. Adjust the opening size until a single rotation drops approximately your target portion.
Timer Setup
The AT1 uses a circular timer dial with 48 peg slots, each representing 30 minutes over a 24-hour cycle. Insert the white plastic pegs at the times you want feedings to trigger. For twice-daily feeding at 8 AM and 7 PM, insert pegs at the 8:00 and 19:00 positions.
Align the dial so the current time lines up with the reference mark on the timer housing. The dial rotates continuously once power is on.
Testing Before You Leave
Always run the feeder for at least 2 days before any extended trip to verify the feeding volume and timing are correct. Watch the fish after each automated feeding. They should consume the food within 2-3 minutes. If there's food floating on the surface 5 minutes after feeding, reduce the portion size. If fish are actively searching for food immediately after, increase it slightly.
Test that the batteries are fresh. With alkaline AA batteries, the AT1 typically runs 4-6 months. Replace them before any trip longer than 2 weeks.
Common Problems and Solutions
Jamming
The most frequent issue with drum-style feeders is food jamming in the dispenser opening. This happens with: - Flake food (too irregular in shape and can clump) - Freeze-dried foods (swell when they absorb humidity from the tank) - Overloaded drum - Pellets larger than 3mm diameter
Stick to sinking or floating pellets between 1-3mm diameter. If you're feeding flakes, switch to a pellet or mini-granule food specifically for use with auto feeders. Hikari Micro Pellets and New Life Spectrum Thera-A in small pellet size both work well with drum-style feeders.
If the drum jams mid-trip, all subsequent feedings fail. Adding a small desiccant packet inside the drum chamber (the type that comes in vitamin bottles) reduces humidity absorption and significantly reduces jamming frequency.
Inconsistent Portion Sizes
If feeding volumes vary day to day, the drum opening is probably loose or the food particle size is inconsistent. Check that the drum collar is snapped firmly into position. For flake food mixtures where some pieces are much larger than others, sift out the large pieces before loading.
Timer Drift
Over weeks, the AT1's timer dial can drift slightly from the set time, causing feedings to occur outside of intended windows. This matters most for fish that get stressed without regular feeding schedules. Check the timer alignment weekly if your fish are sensitive to timing variation.
How the Hydor AT1 Compares to Current Alternatives
Since the Hydor AT1 is discontinued, comparing it to current models is practical if you're deciding whether to track down a used unit or buy something current.
Eheim Everyday Fish Feeder (EHEIM 3581)
The Eheim 3581 is the most recommended automatic feeder by experienced aquarists. It uses the same drum mechanism principle as the Hydor AT1 but adds an integrated fan in the drum to prevent humidity buildup, which is the primary cause of jamming. It programs for 1-8 feedings per day, has a manual feed button, and the drum volume is adjustable. It runs about $35-45 and is widely available.
If you're choosing between a used Hydor AT1 and a new Eheim 3581, buy the Eheim. The moisture fan alone makes it dramatically more reliable.
Orapet Fish Feeder and AutoFishFeeder Models
Budget automatic feeders in the $12-20 range look similar to the Hydor AT1 and use the same basic drum mechanism. They work adequately for short trips (3-5 days) but the build quality is noticeably lower. Timer accuracy can be off by 30-60 minutes after a week, and jamming is more frequent.
Lifegard Aquatics Automatic Fish Feeder
The Lifegard feeder ($45-60) adds a digital LCD display and programmable digital timer, which is significantly more convenient than the peg-dial system on the AT1. You can see exactly when the next feeding is scheduled and program it to the minute rather than to the nearest 30-minute peg interval.
Neptune Systems AFS (Advanced Feeding System)
For reef tanks already running a Neptune Apex controller ($200-250), the AFS integrates directly with the Apex. It pauses all return pumps and powerheads for a set interval before and after feeding so food doesn't immediately go into the overflow. This feature alone is worth the cost for reef tanks where food control matters for water quality. It programs for multiple feedings with different portion sizes and keeps a log of feeding events.
For a full overview of what to pair with an automatic feeder in a complete aquarium setup, see our guide to Top Aquarium Equipment.
FAQ
How long can I leave fish with an automatic feeder?
For healthy, established tanks, 5-7 days is generally safe with a reliable feeder that's been tested beforehand. For trips up to 2 weeks, have someone check on the tank every 2-3 days to verify the feeder is working and the fish look healthy. For trips over 2 weeks, you need a reliable person checking more frequently, not just an automatic feeder.
Do automatic feeders work with freeze-dried food?
Generally no. Freeze-dried bloodworms, brine shrimp, and similar foods are too irregular in shape and absorb moisture aggressively, which causes them to swell and jam drum-style feeders. Stick to consistently shaped pellets or granules. If you want to provide variety, hand-feed freeze-dried foods when you're home and let the auto feeder handle pellet meals.
Can the Hydor AT1 be used with reef tanks?
Yes, with the caveat that any food not consumed quickly in a reef tank degrades water quality. Use the smallest effective portion size, and position the feeder so food falls in an area with good water movement. Some reef keepers turn off their skimmer briefly after feeding to give fish time to eat before the skimmer removes food particles.
My automatic feeder is overfeeding despite being set to the minimum portion. What can I try?
Try loading less food into the drum, around 1/3 full rather than 2/3. With less food pressing against the opening, less falls out per rotation. Also, check that the drum opening adjustment is fully at its smallest setting. Finally, test whether the food particle size is contributing: large pellets that stick in the opening can cause a sudden release of several pieces at once when they finally fall.