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Fish Maintenance

Getting started

  • What sort of tank do I need?
  • How many fish can I keep in my tank?
  • Where is the best place to put my tank?
  • What equipment will I need for my aquarium?
  • Decorating your aquarium
  • Aquatic plants

Keeping fish as pets in your own aquarium is a fascinating hobby.  There are many beautiful fish to choose from – as well as weird and wonderful ones.  Designing the habitat for your aquarium can be great fun and you can be as creative as you like, constructing ship wrecks, ruins and reefs for your fish to find a home in.  Fish as pets have lots of advantages:  they are relatively easy to care for, low maintenance and don't trigger allergic reactions.  Many people find watching fish swimming in an aquarium therapeutic and their vibrant range of colours and patterns are certainly captivating!

Petstop supply a wide selection of both cold water and tropical fish and our trained staff are available to give you advice on keeping fish as pets and the equipment you'll need.  Our range of tanks start at 15 litres and range up to 230 litres as well as starter kits for beginners that contain all the essential equipment for your first tank.   Our check list below will ensure that you have everything you need to get started.

  • View our fish Products section for a selection of tanks and equipment

Check List

  • Fish tank
  • Hood/cover
  • Base/stand
  • Heater (for tropical fish)
  • Filter
  • Lighting
  • Air pump (optional)
  • Substrate (gravel, glass beads, sand)
  • Rocks, pebbles, driftwood
  • Ornaments/decorations
  • Aquatic plants 

What sort of tank do I need?

Tanks come in all sorts of shapes and sizes and cater for both cold water and tropical fish.  They are made from tough acrylic or strong glass and the size of your tank depends on what types of fish you'd like to keep, how many of them and where you plan to put the tank in your home.  

Larger tanks have more stable temperatures and water chemistry which means that your fish will be in a healthier environment.  Another benefit of a large tank is that your fish are more likely to get on with each other as they don't have to compete for space.  

Do I need a base or a stand?

Tanks are very heavy when filled with water and a proper aquarium stand, base or cabinet is essential.  You need one that has been built strong enough to hold the weight of your tank and there are plenty of designs available.  Purpose built stands and bases are also resistant to water damage. 

Do I need a hood or cover?

Keeping a hood or cover on your tank helps to keep humidity levels down and decrease the amount of water you need to replace due to evaporation.   They also shield the water from dust and dirt and prevent fish from jumping out of the tank.  Hoods are also designed to accommodate filters, heating and lighting equipment so that everything is neatly contained.

  • Visit our fish Products section for our range of tanks, covers and stands

How many fish can I keep in my tank?

Your fish will need room to live happily together so you need to work out how many fish you can keep in your tank without overcrowding.  Too many fish can pollute the tank with high levels of harmful chemicals such as ammonia and nitrite, which can poison the fish.

The general rule is to allow 2.5cm (1 inch) of fish to 4.5 litres (1 gallon) of water.   If you have bought young fish to stock your tank with remember they will grow in size so check what their adult size will be. 

View of our Types of Fish section to learn more about the different species of fish available

Where is the best place to put my tank?

As tanks are heavy you need a spot that is stable and level to locate your tank in.  A tank that is too close to a sunny window can suffer problems with increased algae growth.  The tank should be away from hot and cold spots so don't place it too close to radiators or in a direct draught.  You will also need an electric socket nearby as you will need to plug in your equipment such as filters and lighting. 

What equipment will I need for my aquarium?

Do I need a heater?

If you'd like to keep tropical fish you'll need a heater as these fish live in warm water. 

  • Ideally the water temperature should be between 23 - 28°C (74 – 82ºF) and the size (in watts) of your heater will depend on the size of your fish tank.
  • Heaters have thermostats built into them so that they will switch off when the temperature in the aquarium is at the level you have set.
  • If you have a very large tank (over 160 litres) you could put 2 heaters at either end to keep an even temperature throughout the water.  
  • If you are not sure what size of heater you will need our staff will be able to help you in store.

Do I need lighting?

Lighting your aquarium gives your fish a sense of day and night and also helps to display their vibrant colours.  

  • If you have aquatic plants in your tank they will need lighting to grow and thrive.  
  • Lighting should be on for around 10 hours a day and you can use a timer to set the lights to the hours you need.   
  • There are several types of lighting tubes, bulbs and units available and our staff will be able to advise you as to which would suit your tank best.  

Do I need a filter?

You will need a filter system for your tank to keep the water clean.  Filters remove the waste products from the fish, uneaten food and decaying aquatic plant matter.  If the water is left unfiltered the waste will build up to toxic levels and your fish will become sick.  Filters also enrich the water with oxygen by causing ripples which break the surface of the water.  If you spot a white or green hazy cloud in the tank this is a Bacterial or Algae Bloom and your filter will not be able to remove this.  Such blooms can be caused by over feeding causing uneaten food to decay in the tank.  Water changes, algae cleaning and gravel vacuuming can help to treat and prevent blooms.

  • Visit our Setting up your fish tank advice to learn more

There are 3 different types of filters you can use:

  • Under Gravel Filters – (fitted under the gravel).  You will need an air pump to run your under gravel filter.  Although effective these can cause difficulties when you clean them as you disturb the fish and are not recommended if you are growing aquatic plants.
  • Internal Power Filters - (submerged under the water in the tank).  These give a rapid turn over of water but are difficult to hide in the tank.
  • External Power Filters (situated outside the tank).  These can be cleaned without disturbing the fish, don't take up any tank space and some also have heaters installed.
  • Filters use different methods of cleaning the water, sometimes in combination with each other: 
  • Mechanical (filtering through  nylon floss or synthetic foam)
  • Biological (uses beneficial bacteria to break down toxic waste to harmless substances).  Fish excrete Ammonia into the water and this is toxic.  Nitrifying bacteria need to build up in the tank to convert the Ammonia into Nitrite (which is also toxic to fish). As different sorts of bacteria begin to grow in the tank the Nitrite (NO2) is then converted to more harmless Nitrates (NO3).  Biological filters contain the beneficial bacteria (Nitrobacter and Nitrosomona)  that can break down Ammonia and Nitrates and prevent your fish from becoming poisoned.
  • Chemical (uses carbon to clear the water or ammo rocks to absorb ammonia)
  • Visit our Stocking your fish tank advice to learn more

Do I need an air pump?

Air pumps create hundreds of little bubbles which help to oxygenate the water as each bubble increases the surface area allowing oxygen and carbon dioxide to diffuse.   Air pumps circulate the oxygen vertically around the tank and help aerate your aquarium water.  Filters don't aerate in the same way as they break the surface of the water creating ripples.  This increases the surface area of the aquarium water which allows for diffusion of gasses into and from the atmosphere.

Air pumps can also be used for visual effect – they can be attached to airstones, bubble wands and ornaments (treasure chests or divers) to make streams of rising bubbles which some fish like to swim amongst.

  • Visit our fish Products section for our range of aquarium equipment and accessories

Decorating your aquarium

Once you have chosen your tank and equipment you will need to decorate your aquarium.  This is your chance to get creative!  Your fish will need nooks and crannies to hide in and it's a good idea to find out what sort of environment your fish would have lived in their natural environment.  Some fish like to peep out of caves, others like to swim in little shoals protected by rocky outcrops and some will flit in and out of holes in driftwood.  

Petstop have a wide range of substrates (gravels, coloured glass or sand), pebbles, rocks, driftwood, artificial plants and aquatic ornaments to set up the habitat for your fish.  Shop bought items will be safe for your fish as they have been pretreated and will not release toxic chemicals into the water.  

Visit our fish Products section for our range of aquarium accessories
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Aquatic plants

Growing live aquatic plants can be challenging if you are a beginner and you might like to consider choosing a range of artificial plants instead.  However aquatic plants can provide wonderful scenery in your aquarium as well as giving your fish a place to hide and spawn. 

Some fish like to eat certain plants so you'll need to check if your fish belong in this category lest your prized specimens end up nibbled.   
Live plants use up carbon dioxide and give off oxygen during the day but at night this process is reversed.  If you have a lot of plants in your aquarium you might find running an airstone at night helps keep the oxygen balance from being depleted.  
Aquatic plants can also help the habitat in your aquarium as they harbour bacteria that breakdown waste from the fish but they can also harbour water snails or parasites. 
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Setting up your fish tank

  • How do I set up my tank?
  • Tank and water maintenance

Our guide below will help you to set up your fish tank step by step.  Once your fish tank is up and running we recommend that you wait 3 days before introducing any fish to allow the water and filtration system to settle.  

How do I set up my tank?

  • Wash out your tank with warm water – don't use soap or liquid detergents. Your tank needs to be positioned away from direct sunlight and excessive heat (ie not close to a radiator) to prevent major problems with algae.  The tank should also be near to an electric socket to supply the lights and filter with power.  For safety make sure that you create a drip loop with the electric cables.  To make a drip loop all you have to do is to have the electrical cable long enough so that it droops below the electric socket and then back up.  Any water running down the cable will drip down from the loop, rather than running straight into the electric socket. Remember once filled with water your tank will be very difficult to move if it is a large tank!
  • Wash your gravel, ornaments and plants in water before adding them to your tank.  
  • If you are using an Under Gravel Filter place it on the floor of the tank.
  • Layer the gravel on the base of the tank – it should be about 2 inches (5 cm) deep.  Slope the gravel down towards the front of the tank to create depth of field (this also lets debris fall to the front of the tank which makes it easier to remove).  
  • Add your stones, driftwood and ornaments – you can create different zones for the fish, clearings where they can congregate and dwelling places where they can hide.
  • Place a large plate or dish on top of the gravel and slowly fill the half full with cold water.  The plate will stop the water splashing about and disturbing the gravel and altering the positions of your stones.
  • If you are using live aquatic plants add them at this stage.  Position tall plants towards the back of the tank and shorter ones towards the front.  Don't forget to anchor your plants so they don't float back up to the top when the tank is filled!
  • Set up your equipment:  install your heater (if you are keeping tropical fish), filter and air pump.  Make sure that your electrical cables are safe and dry.  
  • Fill up your tank to an inch (2.5 cm) from the top.
  • Tap water contains chlorine so add a water conditioner or dechlorinator to the water.  Water conditioners can also contain a solution that breaks down organic matter to aid in the development of bacteria which will ultimately establish a natural balance in your tank.  You can test the water to see if it is safe for your fish with a water test kit – this will also help you to monitor your water once you have added your fish.
  • Place your hood and light on the top of the tank.  Switch on the electrical equipment.
  • Visit our fish Products section for everything you will need to set up your tank

Tank and Water Maintenance

Changing the water - you will need to change the water in your tank about every 2 weeks but only 15 – 20% needs to be replaced.  

  • Always make sure that the water you add to the tank is the same temperature as the water in the tank and that has been treated with water conditioner to remove chlorine.  

Cleaning filters – filter inserts (floss etc) should be cleaned or changed at least every 4 weeks.  

  • You might find that if you have a lot of fish in your tank you will need to do this more often.  

Vacuum the gravel – your gravel will collect debris from the fish waste, uneaten food and plants so you will need to vacuum it on a regular basis to stop these deposits building up and poisoning the fish.

  • Syphoning sets are available and are useful not only for sucking up deposits but also for syphoning water from the tank during your water changing routine.

Remove algae – algae will build up on the sides of your tank and this can easily be removed by scraping the walls of your tank when changing the water.  There are a variety of tools available to help you do this.  

  • Algae magnets allow you to clean off algae without getting your hands wet – they have non abrasive cleaning pads that can be pulled up and down the sides of your tank by magnetic attraction.   Alternatively you can introduce fish that eat algae that will help to clean your tank such as sucker mouthed catfish or mollies.
  • View our fish Products section for maintenance and cleaning equipment

Feeding your Fish

Types of fish food

There are a wide range of fish foods available from fish flakes and pellets to frozen and freeze dried foods.  Our staff will be happy to advise you on the most suitable food for your fish in store and we stock a number of speciality foods for fish with specific dietary needs.

Fish flakes – ideal for surface and mid level feeders.  They are a popular choice as they are easy to store and don't require preparation.  They are designed to float on the surface of the water and most varieties of flakes are suitable for a wide range of fish species.  There are also algae and spirulina (blue-green algae) flakes for herbivorous fish as well as Flakes made from brine shrimp, earthworm, tubifex worm, bloodworm, water fleas (daphnia) and mosquito larvae.   

  • Fish with smaller mouths may need you to crumble flakes so that they have a chance to compete.

Fish pellets, sticks, granules, tablets, wafers – designed to float or sink depending on the type of fish they are intended to feed.  They come in various sizes and are a good choice for larger fish.  

  • These also have the same ingredients as fish flakes but are good for mid level and bottom feeding fish such as catfish and plecostomus.

Freeze-dried and frozen fish food – great as a treat for many types of fish but are essential for fish that do not take readily to dry foods.  A wide variety of foods are available in this from bloodworm to mysis shrimp.

  • Visit our fish Products section for our wide range of fish foods

How much do I feed my fish?

The best advice is to feed your fish no more than they can eat within 2 minutes.  The reason for this is that uneaten food will decay and contaminate the water.  Most fish keepers feed their fish once or twice a day but you can feed them little and often – as long as all the food is eaten and nothing is wasted.

  • Start by feeding your fish a very small pinch of food and watch to see how long it takes for them to eat it.
  • Observe how much food falls to the bottom, and how long it takes the bottom-dwelling fish to eat it. If after 2 minutes there's not a scrap of food left, put in another pinch.
  • If there is excess food left over at the bottom of the tank after 10 – 15 minutes siphon it out or scoop it out with a net so that it does not pollute the water.
  • Watching your fish eat is also a good way of monitoring their health and appetite.  You may notice that some of your fish are not getting their fair share. You can help by varying the kinds of food offered, giving wafers or pellets to bottom feeders and flakes to surface feeders.   
  • Visit our fish Products section for our wide range of fish foods 

Stocking your fish tank

  • Cycling your tank
  • Stocking your tank
  • How to add fish to your tank

Cycling your tank

Once you have your fish tank set up you need to start the Nitrogen cycle going in the tank.  All new tanks need to establish a cycle to be able to provide a healthy living environment for the fish.  

What is the Nitrogen cycle?

Fish excrete Ammonia into the water and this is toxic.  Nitrifying bacteria need to build up in the tank to convert the Ammonia into Nitrite (which is also toxic to fish). As different sorts of bacteria begin to grow in the tank the Nitrite is then converted to more harmless Nitrates.  

Fishless Cycling

We recommend Fishless Cycling which is done with the aid of products that help you to start the Nitrogen cycle without adding fish:  

  • Filter Boost Water Treatments which encourage the growth of bacteria
  • Ammonia Removers which combat excess ammonia

You can check to see if your tank has cycled successfully with testing kits that measure the Ammonia, Nitrite and Nitrate levels in the water.

  • Visit our fish Products section for a range of water treatments and conditioners

Hardy fish 

Once your tank has stabilised you can start building your community of fish gradually, adding a few at a time.  This way the bacteria in the tank can adjust to the changes and the balance is not upset or overloaded.  There are a few hardy fish which we can recommend to start off with that will tolerate higher amounts of toxins in the tank such as Danios and Mollies.  Our staff will be able to give you accurate advice tailored to your needs in store.

View our Types of Fish section to learn more
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Stocking your tank

You'll need to make sure that the types of fish you have chosen will get along with each other.  Certain types of fish can attack other fish and our staff will be very happy to give you advice about which fish are compatible with each other in store.  

Tropical fish

One good tip is to choose fish that swim at different levels of the tank, which makes the most of the space available and also gives a good display.

  • Top level fish: Common Hatchetfish, Siamese Fighting Fish (Betta)
  • Top to Mid level fish:  Gouramis, Swordtails, Guppies
  • Mid level fish:  Tetra, Tiger Barb, Glassfish
  • Bottom – Mid level fish:  Clown Loach, Discus
  • Bottom level fish:  Corys, Catfish
  • View our Types of Fish section to learn more

Cold Water fish

Some fancy goldfish are slow swimmers and should not be mixed with other goldfish varieties that are fast and agile as they will have a hard time competing for food:

  • Slow Swimmers:    Black Moor, Bubble Eye, Celestial, Chinese Lionhead, Pearlscale, Tosakin, Fantail, Oranda and Veiltails
  • Fast Swimmers:  Common Goldfish, Shubunkin and Comet 

Smaller fish such as the White Cloud Mountain Minnow and the Danios are best kept in schools of 6 or more.  Fully grown fast swimming Goldfish will eat smaller fish like the Minnows and Danios so we do not recommend keeping them together.

  • View our Types of Fish section to learn more

How to add fish to your tank

When you buy your fish, they will be netted and put into a plastic bag, with a little water from their tank.

  • Once home, turn your aquarium lights off as this will help to reduce stressing your new fish.  
  • Rest the bag on the water in your aquarium for 15 minutes.  This lets the water inside the bag adjust to your tank's temperature and avoids giving your fish a shock.
  • Add a small amount of tank water to the bag (this helps to balance the pH and prevent a pH shock to the fish).  Leave for a further 10 minutes.
  • Ideally net the fish out of the bag.  The fish will have defecated in the bag and the water will be full of ammonia, carbonic acid and thus a lower pH so it's not a good idea to add this water to your tank!
  • Leave the fish to settle in for a few hours to get used to their new surroundings.
  • Turn the aquarium lights back on and then give them a little food.

Keeping your Fish Healthy

  • Water quality problems
  • Whitespot / Ich
  • Columnaris / Cotton Mouth
  • Fin Rot / Tail Rot
  • Fungus 
  • Velvet / Rust / Gold Dust Disease

Signs of illness in fish are gasping for air, lethargy (reluctant to swim), spots, red skin and fins, weight loss, abdominal enlargement and inflamed gills.  A lot of fish health problems are related to water quality but fish can develop diseases and our guide will help you to recognise the symptoms.

Water quality problems

If you spot your fish gasping at the water's surface this could be a sign that your fish are struggling to breathe.  Your fish will be at the surface as oxygen concentration is highest where air and water meet.  Other signs of respiratory problems are lethargy, swimming sluggishly and inflamed gills.

Your aquarium could have too much ammonia or nitrite in the water.  Elevated ammonia levels inflame the fish's gills and nitrite poisoning prevents red blood cells from transporting oxygen. The presence of chlorine and pH levels that are too high or too low will also make fish gasp at the surface.  

Test your aquarium water for ammonia, nitrite and pH imbalances. Our staff can  test a water sample for you - we can test for Ammonia, Nitrite, Nitrate and pH in store. We test for all four and will advise you on the best course of action based on the results.  
Check that your heater, filter and air pump are working properly and siphon debris from the gravel to improve biological filtration.  
A water change is usually recommended  but the amount that should be changed depends upon the quality of the water and the frequency of the changes.  If in doubt of the amount of water you should change ask our staff for help and advice.

Whitespot /Ich

Whitespot or Ich (Ichthyophthirius multifiliis) is caused by a protozoan parasite and is very contagious. It can be triggered by poor water quality and stress.  Symptoms are small white spots – about the size of a pin head - on the fish, scratching against hard objects and lethargy.  Whitespot is very common and is easy to treat but you must catch it early as fish can become too ill to recover.  In advanced stages fish can suffer from gill damage and be seen gasping for air.  There are effective liquid treatments available which you add to your tank water.

Columnaris / Cotton Mouth

Columnaris is often mistaken for a fungal infection but is actually a common bacterial infection.   Symptoms are greyish white patches on the mouth, edges of scales, and fins that resemble fungus.  Sores may appear on the body and the gills can become affected.  It is highly contagious and can be triggered by poor water quality or stress.  Anti-bacterial medications are available and should be used promptly.

Fin Rot / Tail Rot

Fin Rot or Tail Rot is a common disease and is caused by several different bacteria.  The symptoms are opaque, fraying and ragged fins and/or tail that become eroded away until the fish dies.  The disease is usually triggered by poor water quality or where fin damage has occurred – often caused by fin-nipping fish.  It's important to catch this disease early and there are antibacterial treatments available.


Fungal spores are always present in the aquarium, and an outbreak of fungal disease usually occurs after damage to the fish and as a secondary infection.  Symptoms are cotton wool like growths on the body.  Anti-fungal remedies are available that can destroy the fungus and prevent it from spreading.

Velvet / Rust / Gold Dust Disease

Velvet (also known as Rust or Gold Dust Disease) is a common disease and is caused by the protozoan parasite Oodinium.  Symptoms are a fine greyish gold to white dust on the body of the fish, rapid gill movement, weight loss and scratching or rubbing the body against hard objects as the fish tries to remove the parasite. Oodinium is usually triggered when the fish are stressed by poor quality water, changes in the water temperature, or being transported.  Medication is available and should be used as soon as possible as Velvet is highly contagious.