How to Safely Remove a Fish From Your Aquarium

Table of Contents

• When You Need to Remove a Fish
• Preparation Before Catching
• 6 Techniques for Removing Fish
• Special Tips for Planted Tanks
• When to Call a Professional
• Frequently Asked Questions

When You Need to Remove a Fish

There are several reasons you might need to catch and remove a fish from your aquarium. None of them are particularly fun, but knowing the right technique makes the process far less stressful for both you and the fish.

• Rehoming – the fish has outgrown the tank, is incompatible with tank mates, or you are downsizing your setup
• Hospital tank transfer – a sick fish needs to be isolated for treatment, especially when medication would harm plants or invertebrates
• Aggression management – a bully needs to be removed to protect other inhabitants
• Tank breakdown – moving house, restarting the tank or performing a major rescape
• Breeding separation – isolating breeding pairs or protecting fry from adults

Whatever the reason, the goal is always the same: remove the fish quickly and calmly with minimum stress to every living thing in the tank, including the plants and other inhabitants you are leaving behind.

Preparation Before Catching

A little preparation goes a long way. Rushing in with a net and chasing a fish around the tank for 20 minutes is the worst approach for everyone involved.

Prepare the Destination First

Before you start trying to catch anything, have the destination ready. If you are moving the fish to a hospital tank, that tank should already be set up, filled with treated water and at the correct temperature. In Singapore, where ambient water sits at 28-32 degrees Celsius, temperature matching is usually straightforward as long as both tanks are in the same room.

Gather Your Equipment

• Two appropriately sized nets (the fish should fit comfortably inside with room to spare)
• A clean bucket or container with tank water
• A towel to cover the bucket (prevents jumping)
• Optional: a clear plastic container or fish trap

Turn Off the Lights

Dimming or turning off the tank lights for 10-15 minutes before attempting to catch a fish calms them down noticeably. Fish are less alert and less likely to dart away in subdued lighting. Close curtains or blinds if natural light is strong.

Skip the Feeding

Do not feed the fish before catching. A hungry fish is more likely to cooperate with food-based trapping techniques. An empty stomach also reduces the risk of the fish regurgitating from stress during the catching process.

6 Techniques for Removing Fish

1. The Two-Net Method

This is the most commonly used technique and works well for most small to medium fish.

1. Hold one net still in the tank, positioned where you want to guide the fish towards.
2. Use the second net to gently herd the fish towards the stationary net.
3. When the fish swims into or near the stationary net, scoop it up with a smooth, confident motion.
4. Transfer the fish immediately to a container of tank water.

The key is patience. Use the herding net slowly and steadily. Quick, erratic movements spook fish and trigger their escape response, making them dart into hiding spots and stirring up the entire tank.

2. The Container Method

For fish that are easily spooked by nets, a clear plastic container works surprisingly well.

1. Submerge a clear plastic container (a clean food container works) in the tank at an angle.
2. Sprinkle a small amount of food near the container opening.
3. Wait for the target fish to swim inside to eat.
4. Slowly tilt the container upright and lift it out of the water.

This method is calm, low-stress and avoids net contact, which can damage delicate fins or remove the protective slime coat. It works exceptionally well for bettas, gouramis and other fish that approach food confidently.

3. DIY Bottle Trap

For fast or shy fish that refuse to be netted, a bottle trap catches them without your active involvement.

1. Take a clean plastic bottle (500ml or 1.5 litre depending on fish size) and cut the top off just below where it starts to narrow.
2. Invert the cut top piece and push it back into the bottle, creating a funnel entrance.
3. Place food inside the trap and submerge it in the tank.
4. Leave it overnight or for several hours. Fish swim in through the funnel to reach the food but cannot easily find their way out.
5. Remove the trap with the fish inside.

This is particularly effective for small, fast species like danios and small rasboras that can outswim any net in a planted tank full of hiding spots.

4. Draining the Water Low

When other methods fail, partially draining the tank makes catching much easier.

1. Remove about 50-70 percent of the water into clean buckets using a siphon.
2. With less water, the fish has less room to evade and cannot dive deep to escape.
3. Use a net or container to catch the fish in the shallow water.
4. Return the water to the tank immediately after catching.

This is effective but more disruptive. Use it as a last resort for particularly difficult catches, and be careful not to expose plants or hardscape to air for too long, especially in Singapore’s warm climate where exposed surfaces dry quickly.

5. Catching at Night

Many fish species sleep or become very still at night. Some rest on leaves, the substrate or inside decorations, making them easy to catch.

1. Wait until the tank lights have been off for at least two hours.
2. Approach the tank quietly with a dim torch or use your phone light on the lowest setting.
3. Locate the fish. Many will be hovering motionless near the bottom or on plant leaves.
4. Place a net or container beneath the fish and scoop upwards in one smooth motion.

This method works brilliantly for tetras, rasboras and corydoras. It is less effective for nocturnal species like plecos, which are most active after dark.

6. Cornering With Dividers

For larger tanks where fish have enormous amounts of space to flee, you can section off the tank.

1. Use a piece of clean acrylic, a tank divider or even a large net stretched across the tank.
2. Gradually move the divider to compress the fish’s available space into a smaller section.
3. Once confined to a small area, use a net or container to catch the fish.

This is how professional aquarium maintenance teams often work when servicing large tanks in offices and commercial spaces around Singapore.

Special Tips for Planted Tanks

Catching fish in a heavily planted aquascape presents unique challenges. The plants provide countless hiding spots, and aggressive netting can destroy weeks of plant growth.

• Avoid dragging nets through stem plants. Nets catch on stems, uprooting them and snapping delicate species. Guide the fish to open areas of the tank before attempting to net.
• Protect your carpet. Stepping into the aquascape with nets or hands can crush dwarf hairgrass, Monte Carlo or other carpeting plants. Work from above and use long-handled tools.
• Mind the hardscape. Dragon stone and Seiryu stone can snag net mesh. Use fine-mesh, frameless nets that are less likely to catch on rock edges.
• Prefer trapping over chasing. In a planted tank, the bottle trap or container method causes far less collateral damage than chasing with nets.
• Accept some disruption. Even with the best technique, catching a fish in a heavily planted tank will cause some disturbance. Replant anything that gets uprooted immediately after the catch.

When to Call a Professional

Sometimes the smart move is to call in help. Consider professional assistance when:

• The tank is very large – tanks of 200 litres or more with dense planting can take hours to catch a single fish by yourself
• The fish is large or aggressive – large cichlids, arowanas or fish with sharp spines pose injury risks
• You have an expensive aquascape – the risk of destroying a premium layout during a difficult catch may exceed the cost of professional help
• Multiple fish need removing – a full restocking requires systematic catching that professionals do efficiently
• The tank is a custom built-in installation – limited access panels make catching difficult and risk damage to cabinetry

Professional aquarium maintenance services have specialised equipment, experience with tricky catches and the skills to do it without damaging your setup. This is especially relevant for high-end aquascapes and custom installations common in Singapore condos and commercial spaces.

Frequently Asked Questions

How long can a fish stay in a bucket during transfer?

A fish can stay in a clean bucket of tank water for several hours without issues, provided the water is at the correct temperature and the bucket is covered to prevent jumping. For longer holds, add a small air stone connected to a battery-powered pump. In Singapore’s heat, place the bucket away from direct sunlight to prevent rapid temperature spikes.

Will catching fish stress my other fish?

Yes, the catching process can stress the entire tank. Chasing, netting and hands in the water create commotion that alarms all inhabitants. This is why the calmest, fastest technique is best. After removing the target fish, leave the tank lights off for a few hours and skip feeding until the next day to let everyone settle.

Can I use chemicals to sedate fish for easier catching?

Clove oil is sometimes used to lightly sedate fish for catching, but this is generally unnecessary for home aquariums and carries risks if the dosage is wrong. It is a technique best left to veterinary professionals and experienced fish keepers. For most situations, the mechanical catching methods described above are safer and effective.

How do I catch shrimp without catching fish?

Shrimp traps baited with a small piece of blanched vegetable work well. Shrimp are attracted to the food while most fish ignore vegetables in favour of their regular diet. Commercial shrimp traps are available at aquarium shops along Serangoon North Avenue 1 and Clementi. Leave the trap in overnight for best results.

For more tips on fish handling, read our guide on how to catch fish in an aquarium for additional techniques and species-specific advice.

Dealing with a difficult catch or need to rehome fish from a complex setup? Our aquarium maintenance team handles fish removals across Singapore, from nano tanks to large custom installations. Visit us at 5 Everton Park or contact Gensou to arrange a service call.