Guide
Aquarium care on holiday: do's, don'ts, and how to prepare
Going away? Your fish don't take holidays. Here's how to keep your tank healthy while you're gone - and the mistakes that cost fish their lives.
- Healthy adult fish can go 3-7 days without food. A week away with no feeding is usually safer than leaving food with an unreliable helper.
- Do a 40-50% water change 1-2 days before you leave. Start with the cleanest possible water, not a scramble the morning of departure.
- Never feed extra "just in case." Uneaten food rots, spikes ammonia, and kills fish faster than hunger ever would.
- Automatic feeders work well for trips up to two weeks - if you test them for several days before you leave, not on the day.
- Fish sitters need pre-portioned food and a hard upper limit. A well-meaning friend overfeeding every day is a genuine threat to your tank.
- Trips longer than two weeks need a proper plan: a knowledgeable sitter, partial water changes mid-trip, and equipment checks.
How long can your fish actually go without you?
Most healthy adult fish in a stable, cycled tank handle 3-7 days without food without issue. Many species comfortably stretch to 10-14 days. The real limiting factors are not hunger - fish are metabolically flexible and deal with short fasts far better than mammals - but water quality drift, equipment failure, and overfeeding by whoever you leave in charge.
For a weekend or a short week, a well-maintained tank with no feeder and no sitter is often the safest option. For 10-14 days, an automatic feeder is your best tool. Beyond two weeks, you need someone capable of doing a water change and spotting a problem - not just someone willing to sprinkle food in daily.
Beyond this, nitrates accumulate enough to stress fish even in a healthy tank, and the risk of equipment failure going unnoticed becomes real.
What to do before you leave
Water change: timing matters
Do a larger-than-normal water change - 40-50% - one to two days before you go. This resets nitrates, removes dissolved waste, and gives you a clean baseline. Do not leave it to the morning of departure; you want the tank to settle and confirm everything is stable before you walk out the door. If you want to understand why this matters chemically, the nitrogen cycle explained covers what's actually building up in your water between changes.
Test everything and write it down
Test ammonia, nitrite, nitrate, and pH before you leave. If anything is off - any ammonia or nitrite reading above zero, nitrates above 40 ppm, pH outside your fish's preferred range - fix it before you go, not when you get back. Logging your baseline means that if something goes wrong while you're away, a knowledgeable friend or vet can compare against your normal readings. The aquarium water parameters guide has the target ranges for common species if you need a reference.
Log your pre-holiday test results in App-aquatic so you have a timestamped record. If your tank sitter notices something odd, they can show the numbers to anyone helping remotely without having to guess what "normal" looks like for your setup.
Clean the filter - but not too close to departure
Rinse your filter media in old tank water (never tap water - chlorine kills beneficial bacteria) about a week before you leave. This removes accumulated sludge that would otherwise break down and release ammonia while you're gone. The reason for the one-week gap: cleaning disrupts your bacterial colony slightly, and you want it fully recovered before you disappear. Do it the day before you leave and you're adding unnecessary risk to an already-busy situation.
Trim plants and remove debris
Dead or dying plant matter breaks down into ammonia. Before you go, pull out any visibly rotting leaves, trim overgrown stems, and remove any uneaten food or waste you can see. A clean tank on departure day drifts much more slowly than one with organic material already decomposing.
Check every piece of equipment
Heater, filter, and light timer. A heater that's been running fine may fail when it's under sustained load for two weeks with no one checking. If your heater is old or has been acting inconsistently, replace it before you leave - not after you get back to a cold tank. Set your light timer if you haven't already; a consistent photoperiod reduces fish stress and keeps algae from getting ahead of you while you're gone.
A failed heater in a tropical tank can crash temperatures within hours. If your heater is more than three years old and you're going away for more than a few days, a backup heater is a reasonable precaution - they're cheap compared to restocking a tank.
The overfeeding problem
This is where most holiday tank disasters actually start. The instinct to feed extra before you leave - or to ask someone to feed generously "just to be safe" - is the single most reliable way to kill fish while you're on holiday.
Uneaten food sinks, rots, and produces ammonia. Ammonia spikes stress and kill fish. A healthy, cycled tank with no food added for five days is in significantly less danger than a tank fed double portions by a helpful neighbour every day. If you're leaving for less than a week, seriously consider feeding nothing at all rather than relying on someone who doesn't keep fish.
Giving your fish sitter an open container of food and saying "feed them once a day." Without guidance on portion size, most people massively overfeed. Pre-portion every single feeding into small labelled bags or containers before you leave, and tell them explicitly: one bag, one feeding, nothing extra.
Automatic feeders: the honest assessment
Automatic feeders are the right tool for most trips of more than a few days. They dispense a consistent small portion on a timer, they don't get anxious that the fish look hungry, and they don't add "just a little extra" because the fish are swimming near the surface. For trips up to two weeks, a good feeder is more reliable than most human helpers.
What they're good at
Consistency. A feeder set to dispense a small amount of pellets or flake once or twice a day will do exactly that, every day, without variation. That predictability is genuinely better for water quality than the erratic feeding patterns most sitters produce.
What goes wrong
Three things fail: the feeder jams (common with flake food, less so with pellets), the drum runs empty, or it's set to dispense too much. Pellets are more reliable than flake in almost every feeder on the market - flake clumps and blocks the mechanism. Set the portion smaller than you think is necessary; you can always adjust, but you can't un-rot food that's already in the tank.
Run your automatic feeder for at least five days before you leave, watching each dispensing cycle. Check that the amount landing in the tank is being eaten within two minutes. If there's food left on the surface after two minutes, reduce the dose. Do this well before departure, not the night before.
Feeders and humidity
Most feeders mount on the rim of the tank. Humidity from the water rises into the drum and can clump or spoil the food inside, especially in a warm room. Some feeders have a sealed drum with a desiccant chamber - worth paying extra for if you're going away for more than a week.
Using a fish sitter
A fish sitter is the right call for trips over two weeks, for tanks with sensitive or high-value fish, or any time you don't trust your equipment to run unattended. The key is setting them up to succeed rather than leaving them to guess.
What they actually need to do
Be honest about the scope. Most fish sitters don't need to do water changes for trips under two weeks if you've done a large change before leaving. What they do need to do: show up, confirm the filter is running, the heater is on, and no fish are dead or visibly sick. Feed from pre-portioned containers. That's it. The more you ask of someone who doesn't keep fish, the more risk you introduce.
For trips over two weeks, you need someone willing to do a 20-25% water change partway through - or someone who keeps fish themselves. Walk them through it before you leave, with the dechlorinator already measured out and labelled.
Leave written instructions, not verbal ones
Write down: what to feed and how much (ideally just "one bag from the labelled box"), what normal looks like for the tank, what to do if the filter stops (restart it), what to do if a fish dies (remove it, don't leave it in), and an emergency contact - you, or someone else who knows aquariums.
Most fish sitter disasters happen because the owner felt guilty asking for less. A sitter who checks in every two days and feeds sparingly is more valuable than one who visits daily and feeds with enthusiasm. Under-asking is better than over-relying on someone without the background to recognise a problem early.
Species that handle absence better or worse
Hardy, adaptable species - most livebearers, zebra danios (Danio rerio), white cloud mountain minnows (Tanichthys albonubes), and common plecostomus (Hypostomus plecostomus) - handle two-week gaps well in stable conditions. If you're stocking a tank specifically with holidays in mind, the best fish for beginners includes most of the genuinely resilient species.
Fish that need more management: discus (Symphysodon spp.), which prefer stable temperatures in a narrow 28-30°C (82-86°F) range and feed multiple times daily; axolotls, which need cooler, well-oxygenated water and regular feeding; heavily planted tanks with CO₂ injection, which need the system maintained; and any tank that's had recent disease, new additions, or is still cycling. If your tank isn't fully cycled before you go, do not leave it unattended - see the how to cycle a fish tank guide first.
What most holiday guides miss
The focus is always on feeding. The less-discussed risks are evaporation and top-off, and CO₂/oxygen balance in planted tanks.
In a warm room over two weeks, an uncovered tank can lose several centimetres of water to evaporation. As water level drops, the filter intake may run dry, the heater may operate at the waterline, and salinity (in hard water areas) creeps up as minerals concentrate. If you're going away for more than a week, either use a cover, ask your sitter to top up with dechlorinated water, or invest in an auto-top-off (ATO) device if your setup justifies it.
On planted tanks with pressurised CO₂: turn the CO₂ off or set it to the minimum before you leave. Excess CO₂ with no one monitoring pH can drop acidity to dangerous levels. With lighting on a timer and CO₂ running unattended for two weeks, you're taking an unnecessary risk.
Track your parameters and get care reminders with App-aquatic.
Get the free appCan I leave my fish for a week without feeding?
Yes, for most healthy adult fish in a cycled tank. A week without feeding is far less risky than leaving food with someone who'll overfeed. Fry, juvenile fish, and species that naturally feed constantly (like discus) are exceptions - they need feeding even on short trips.
Are automatic fish feeders reliable enough to trust?
Good quality feeders are reliable for up to two weeks if you test them properly beforehand and use pellets rather than flake. The failure modes are jamming, overfeeding, and humidity-damaged food - all of which a proper test run before departure will catch.
Should I do a water change right before I leave?
Yes, but one to two days before departure rather than on the morning you leave. A 40-50% change resets nitrates and gives you clean water to start from. Doing it the day before also gives you time to confirm the tank is stable before you go. For guidance on how often to change water normally, see the water change frequency guide.
What do I tell a fish sitter who's never kept fish?
Keep it simple: pre-portion every single feeding before you leave, leave written instructions (not verbal), tell them what a functioning tank looks and sounds like, and ask them to contact you immediately if the filter has stopped or a fish has died - not to troubleshoot it themselves. Less responsibility given to an inexperienced sitter means fewer opportunities for things to go wrong.
How long is too long to leave a fish tank unattended?
With a good automatic feeder and a stable, well-maintained tank, two weeks is a reasonable upper limit for most setups. Beyond that, nitrates accumulate to stressful levels, equipment failure goes unnoticed long enough to cause real damage, and evaporation becomes a meaningful problem. For trips over two weeks, arrange a sitter who can do at least one partial water change.
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