Vacation fish feeder or not? How to leave your fish when you go away

Healthy adult fish in an established tank can go a few days without food with no harm, and most can manage about a week. For longer trips, a tested automatic feeder or a friend with pre-portioned daily packets works better than a vacation feeder block, which can foul the water.

The bigger risks while you're away are usually not hunger. They are a failed heater or filter, a power cut, or a well-meaning friend pouring in far too much food. A little planning covers all of these.

How long can fish go without food?

Healthy adult fish: 2–4 days without food is no problem for almost any established tank. Many healthy adults cope with about a week. Some sources say up to two weeks, but that is pushing it for small, active fish, and opinions differ.
Large, slow fish and cold-water fish (such as goldfish in a cool room) usually cope better than small, fast tropical fish.
Fry and juveniles: they need food every day, often several times a day. Don't leave fry for more than a day or two without someone feeding them.
Predatory fish may start eating smaller tankmates if they get too hungry.
Sick, thin or newly bought fish shouldn't be left unfed. Avoid buying new fish in the two weeks before a trip.

When it's a problem

A weekend or long weekend: no feeder needed for healthy adults.
About a week: most adult fish are fine, but an automatic feeder or one visit from a friend is a sensible extra.
More than a week, fry, or a sick fish: arrange feeding and someone to check the tank every two or three days.
Summer trips: plan for heat too; see heatwave.

Step by step: before you go

Two weeks before: don't add new fish or make big changes.
One week before: set up and test the automatic feeder, if you're using one. Watch how much it drops for several days, and adjust it.
2–3 days before: do a normal partial water change (about 20–30%), vacuum the gravel and rinse the filter sponge in tank water if it's clogged. Doing it a few days ahead, not the day before, gives you time to spot a problem (a heater knocked off, a filter that didn't restart, cloudy water).
Check the equipment: heater working and set right, separate thermometer reading correctly, filter flowing well, air pump running. Replace anything that looks tired.
Set the lights on a timer (around 8–10 hours a day). Lights left on all the time grow algae; lights left off all the time stress fish and plants.
Top up the water so evaporation doesn't drop the level below the filter intake or the heater's minimum line.
Feed normally, or slightly less, in the last few days. Don't "feed them up" the day you leave; extra food mostly ends up rotting in the tank.
The day you leave: check the temperature, check the filter is running, count your fish, and make sure the lid is on.

What to do while you're away

Automatic feeders

A battery or plug-in feeder that drops dry food on a schedule is the best option for most trips of a week or more.
Test it first. Feeders can jam with damp food or drop far too much at once. Set it to give less than you normally feed.
Mount it where moisture from the tank won't clump the food (a small fan or air gap helps), and use dry pellets or flakes, not crumbs.
Even with a feeder, it's worth having someone look in every few days to check the feeder hasn't jammed or emptied the whole load in one go.

Feeder blocks

"Vacation" or "weekend" feeder blocks slowly dissolve to release food. Most experienced keepers avoid them. Many fish ignore them, and the parts that aren't eaten break down and can raise ammonia or cloud the water, sometimes enough to cause a mini cycle.
If you use one, try it while you're home first to see what it does to your water, and use it only in a well-filtered tank that isn't overstocked.

A friend or sitter

The most common holiday disaster is a kind friend feeding a big pinch every day "because the fish looked hungry". Fish always look hungry.
Pre-portion the food. Use a weekly pill organiser, or small labelled bags or containers, one per feeding day. Give a bit less than you'd feed yourself.
Leave short written instructions: which container on which day, "only the food in the box, nothing extra", what the thermometer should read, and what to do if something looks wrong.
Leave your phone number and, with their permission, the number of an experienced fishkeeper or a local fish store.
Show them how to switch off and unplug equipment safely in an emergency (see electrical safety).

Products that help

Automatic fish feeder: drops a set amount of dry food on a timer. Best for trips of a week or more. Test it before you go.
Weekly pill organiser: the easiest way to pre-portion food for a friend.
Light timer: keeps the day-night cycle normal.
Digital thermometer with a high/low alarm: catches heater failures early. Some can send alerts to your phone.
External temperature controller: cuts the heater if it sticks on; see heater overheating.
Battery-powered air pump: keeps oxygen up if the power goes out; see power outage.
Keep on hand: water conditioner, a test kit, and spare food in a sealed container for the sitter.

When you get back

Count your fish and look for any that are thin, hiding or sick. Check behind decorations for any that died.
Check the temperature, filter and water level.
Test ammonia, nitrite and nitrate.
Do a partial water change and vacuum up any uneaten food.
Go back to normal feeding over a few days. Don't make up for lost meals with one big feed.
Clean the glass if algae grew while you were away; see algae.

Common mistakes

A big water change or a filter deep-clean the day before you leave.
Overfeeding before you go, or letting a sitter overfeed. See overfeeding.
Trusting an untested automatic feeder.
Using feeder blocks in a small or crowded tank.
Adding new fish just before a trip.
Leaving the lights on 24 hours a day.
Leaving fry without a feeding plan.

When to get help

If you come home to dead fish, cloudy water or a smell, treat it as a water emergency: see ammonia, cloudy water and smells.
For long trips with fry, breeding fish or a large fish room, ask a fishkeeping club or local store whether an experienced member can fish-sit.
For general feeding advice, see how often to feed fish.

In the game

Multiple Tank Syndrome doesn't have a vacation card yet; the closest risk while you're away is the "City power failure" card.