All FAQs (Helpie FAQ)

If an aquarium filter doesn’t run continuously, several issues can arise:

• Water quality declines: Filters remove harmful waste, toxins, and debris. When off, these substances build up quickly, harming fish health.
• Oxygen levels drop: Filters often help circulate water and promote oxygen exchange at the surface. Without continuous flow, oxygen levels may decrease.
• Ammonia and nitrite spikes: Without constant filtration, toxic ammonia and nitrite can accumulate, stressing or even killing fish.
• Algae growth: Stagnant water encourages excessive algae, which can cloud the tank and disrupt the ecosystem.

For most aquariums, especially those with many fish, keeping the filter running 24/7 is essential for maintaining a healthy environment.

Prepare the Aquarium Ahead of Time

• Perform a partial water change and clean the tank a day or two before leaving.
• Remove any leftover food and debris to keep water quality stable.
• Ensure all equipment like filters, heaters, and air pumps are working properly.

Manage Feeding

• Avoid overfeeding before you leave; most fish can go several days without food.
• Use an automatic feeder to provide regular meals if you’ll be away for more than a couple of days.

Control Lighting

• Set aquarium lights on a timer to maintain a consistent day-night cycle and reduce stress for your fish.

Arrange Care Assistance

• For longer trips, ask a trusted friend or pet sitter to check on your aquarium. Provide clear instructions on feeding and equipment care.

Check Temperature Settings

• Make sure your heater is functioning correctly and set to the appropriate temperature for your fish species.

If the aquarium air pump is not running continuously, oxygen levels in the water can drop, especially in tanks without sufficient surface agitation or plant life. This can stress fish and other aquatic creatures, potentially leading to breathing difficulties or even death.

However, in some well-planted or heavily filtered aquariums, continuous air pumping may not be necessary because plants produce oxygen during the day. Still, for most tanks, especially those with high fish loads, keeping the air pump running consistently helps maintain proper oxygen levels and water circulation.

Running aquarium lights continuously—24 hours a day—can cause several problems. Prolonged lighting encourages excessive algae growth, which can cloud the water and harm plants and fish. It also disrupts the natural day-night cycle that fish and plants rely on, potentially causing stress to your fish and affecting their behavior and health.

To keep your aquarium healthy, it’s best to provide a regular lighting schedule that mimics natural daylight, typically 8 to 12 hours of light per day. Using a timer can help maintain this consistent cycle easily.

Fish are fascinating creatures with unique ways of sleeping. Unlike humans, fish don’t have eyelids, so they don’t close their eyes when they rest. Instead, they enter a restful state where their metabolism slows down and activity decreases. This period of rest is essential for conserving energy and allowing their bodies to heal and grow.

Different species have different sleeping habits. For example, bettas and angelfish often seek out quiet, sheltered spots behind plants or decorations. Meanwhile, clownfish and wrasses may bury themselves in the sand or hide in crevices to rest safely.

Feed your fish only as much as they can eat within 2–3 minutes (in an established aquarium), typically two to three times a day. Remove any uneaten food promptly to prevent waste buildup, which can harm water quality and be toxic to your fish.

For more details, see our article Feeding Your Fish.

We do not recommend flushing fish or other livestock down the toilet. Instead, please wrap them in a paper towel and dispose of them in the trash bin.

n most cases, removing fish from their familiar environment can do more harm than good. A separate tank often has different water conditions, filtration, and temperature, which can cause unnecessary stress and make recovery more difficult.

If you’re worried that your sick fish is being bullied by tankmates, consider using a large floating fry net to gently separate it while you treat the underlying issue in the main aquarium.

Jumping or other erratic behavior is often a sign that your fish is stressed or uncomfortable. This can happen after being moved or disturbed, but it may also indicate poor water quality.

Use an aquarium test kit to check your water parameters and take the appropriate steps to correct any issues.

To identify the exact cause and find the best treatment, visit our Fish Doctor tool for a full diagnosis and expert guidance tailored to your tank.

Flicking or scratching against decorations is often a sign of poor water quality. Use an aquarium water test kit to check the water parameters and take corrective action as needed.

In some cases, this behavior may indicate a parasitic infection. If parasites are the cause, you’ll usually see additional symptoms like small white spots (Ich) or visible parasites on the fish’s skin or fins.

To identify the exact issue and find the best treatment, visit our Fish Doctor tool for a diagnosis and tailored advice for your aquarium.

If your fish are becoming ill, dying, or showing signs of distress, it’s essential to test your aquarium water using a reliable water test kit. Many common water quality issues aren’t visible to the naked eye but can seriously affect your fish’s health.

Prevention is always better than cure. Maintaining proper aquarium care and choosing healthy fish from the start can go a long way in avoiding problems.

That said, illness and fish health issues can arise for a variety of reasons—from poor water conditions to stress, disease, or improper diet.

To find out what’s affecting your fish and how to treat it, visit our Fish Doctor tool. Then, read our article Understanding the Causes of Fish Sickness and Stress to help prevent future issues and keep your aquarium thriving.

Green water is usually caused by microscopic algae suspended in the water. These algae thrive when there’s too much light or excess nutrients in the tank.

To help fix the problem, start by testing the water for high nitrate levels. If the readings are elevated, perform partial water changes and consider adding live plants—these naturally compete with algae by absorbing the nutrients they need to grow.

Make sure your aquarium isn’t placed in direct sunlight, and always turn off the tank lights at night to mimic a natural day/night cycle.

Check for algae growth on the inside of the glass as well—this is often a different type of algae. If you see any, remove it with a magnetic aquarium glass cleaner.

For more tips and in-depth guidance, read our article: Understanding and Treating Green Water in Your Aquarium.

Cloudy, or milky water can occur due to several reasons:

1. General dirt and dust – usually introduced via the gravel or substrate. Ensure your filter is working well and the cartridge is replaced when it looks dirty. Using a product that clumps small particles – such as Quick Clear – will help speed up this process.

2. Poor water quality. Although most water quality issues are invisible, there are occasions when the health of the water becomes visible and turn the water cloudy. It is important to test your water with an aquarium water test kit to establish if there are any underlying problems that need addressing. Carry out your regular water changes to maintain clean, healthy water.

3. Overfeeding or over stocking the aquarium can also cause the water to be filled with dirt particles. Only feed your fish 2-3 times a day (in a mature aquarium) and only enough that they will eat in a few minutes. Any uneaten food should be scooped out with a net. See feeding your fish for more information.

Only add the recommended amount and size of fish, see How many fish.

The general rule is 1cm of tropical fish (adult size) per 1 litre of water, for cold water fish reduce this to 0.5cm of fish per litre – see our article on fish stocking levels for further advice.

Some good options include goldfish, guppies, tetras, and platys. These fish are hardy and easy to care for, making them ideal for those new to fish keeping.

Goldfish are a popular choice for beginners, because they are hardy and can tolerate a wide range of water conditions. They also have a long lifespan (up to 15 years) and come in many different colors and varieties.

If you’re new to fish keeping, it’s best to start with a small number of fish to ensure that you can properly care for them. Starting small will allow you to learn the basics of fish care and ensure that your tank and fish stay healthy.

The term ‘cycling’ is used to refer to the process of getting the filter started and mature with the correct level of good bacteria that process fish waste.

It refers to the natural process ‘The Nitrogen Cycle‘ that we generate in the aquarium to break down the poisonous fish waste into safer compounds.

Watch our short Nitrogen Cycle video that explains the process.

In new aquariums, the filter is not biologically mature. This means the essential bacteria required to nitrify – or clean – the toxic waste produced by fish have not yet become established on the filter media and the water can become unsafe for your fish.

To give this process a head-start, we recommend the use of a filter booster additive such as Fast Filter Start. Filter Boosters add bacteria to the filter, which reduces the time usually required to mature a filter.

Visit our pages on the Nitrogen Cycle and New Tank Syndrome to understand what goes on in a new aquarium and the best way to prevent early problems.

The Nitrogen Cycle is a naturally occurring cycle driven by the biological filter in your aquarium which processes waste in the water.

Watch our short video that explains the process.

Fish keeping FAQs

Here are the answers to the questions we get asked the most about keeping fish. You’ll be an expert in no time!

I don’t know what’s wrong with my fish, what should I do?