Keeping Fish

If you are considering keeping marine (salt water) fish as pets or as a hobby, there is a lot to think about…

Fish are amazing animals and many people enjoy keeping them, however fish need a lot of specialist equipment to help them to survive and flourish in their new homes. Here at the National Marine Aquarium we have a team of dedicated biologists that look after all of our animals. Many people are drawn to fish keeping for a variety of reasons; but here we strive to keep our fish as happy and healthy as possible to help bring our marine conservation messages alive.

Our animals act as ambassadors for their species and allow us to help protect rare animals and endangered habitats by telling the ocean’s story to all of our visitors.

But before we put any animals on display at the Aquarium, here are some of the things that are discussed.

Ethical Fish Keeping

Space and natural behaviour

There needs to be sufficient space for the animal.

  • We have to think about its maximum size – how large will the animal grow?
  • Some animals are highly sociable – think shoaling fish! Other creatures like to live in smaller groups or with other species. We ensure that sociable creatures are only put into exhibits when there is enough space for multiple animals.
  • Additionally it is important to consider other spatial requirements that the animal will need. Some animals can be highly active so will need lots of open space for free movement and foraging, whilst others are drawn to small hiding spaces.
  • We also consider how predator and prey species will interact in mixed exhibits – is there enough room for them to live together?

Providing enough space for the animals encourages natural behaviour and increases the health and wellbeing of the animal.

Aquarium Trade

An important question to ask is ‘where is my fish from?’. The two sources of fish for your aquarium will either be captive bred or wild caught fish.


  • Captive bred fish prevents fish from being taken from the wild and creates a sustainable solution to fish keeping.
  • However, not all fish can be bred in captivity as they have very particular breeding conditions. We ensure that we check the source of all of our captive bred fish and only


  • There are many negative thoughts associated with wild caught fish being used in the aquarium trade; however, if fish are caught sustainably, there can be positive aspects of wild caught fish.
  • Putting a value on wild caught fish can actually help to protect wild species and their homes. Local villagers will help to look after these animals and their habitat if there is a monetary reward for suppling aquarists with the animals.

Responsible Fish Keeping

Salt Water

  • All of the animals here at the National Marine Aquarium are saltwater animals, and we are lucky enough to get our sea water straight from the ocean in Plymouth Sound. Saltwater fish can be very sensitive to changes in salinity, and so you need to ensure that you have the right salinity level in the water for the particular species that you are keeping.
  • Simple refractometers, which measure salinity, are available from most aquarist shops.

Water Quality

  • All living creatures produce toxic waste, and for an animal living in an enclosed aquarium it is important to ensure that this waste is taken out of the water. In the ocean there are special bacteria that can turn the toxic waste into useful products, and it is important to allow this to happen in an aquarium.
  • The filters at the National Marine Aquarium are extremely efficient at removing waste products from the water.
  • We would never consider placing a creature in a tank with no filtration system. As our senior biologist says “keep the water, not the fish!”


  • All animals need to food to survive, and a high quality of nutrition can greatly improve the lifestyle and appearance of a fish. Some fish enjoy eating plants and some fish enjoy eating small animals, so it is important to know the dietary requirements of the fish that you are keeping. We undertake lots of research and information sharing with other public aquariums to ensure we are using the most up-to-date knowledge about the feeding requirements of our animals
  • Many fish enjoy eating flakes and pellets but many species enjoy a variety of food, and if you can match their diet closely to what they would eat in the wild you will notice their colours will become much more vibrant.


  • It is important to make sure that animal’s feel at home in their aquarium environment and the best way to do this is to mimic their natural environment.
  • It is also a good idea to think about which are the best tank mates for your fish. Keeping animals that live in the same natural habitat together will help to reduce stress and ensure that they all get on.

Top things for you to consider….. 


  • The cost of buying the tank and stand could run into the thousands of pounds.
  • Other equipment such as filters, lights etc can be very expensive.
  • Can you afford the extra electricity bill? Your tank set up will need to be on 24 hours a day, 365 days a year and will be running a filter, pump, air stone, lights and heater or chiller.
  • Marine fish can be very expensive – can you afford to purchase enough tank mates for sociable species?
  • Water chemistry packs aren’t too expensive, but refractometers and thermometers will add extra cost.
  • Can you afford to buy the environmental enrichment for your fish? Things like live corals can be VERY cost prohibitive. Rocks, gravel and other items will also add cost to your set up.
  • Can you afford to purchase high quality food for your creatures?

Time and transport

  • Do you have the TIME to look after these creatures; you’ll need to do daily checks on animal behaviour and feeding, regular water changes, water chemistry testing as well as other daily, weekly, monthly and yearly tank maintenance.
  • When you first purchase your tank you will need to fill it and allow it to settle for at least a month to allow a bacterial population to establish itself – are you happy to wait?
  • Some fish can live for many, many years – are you prepared for this responsibility?
  • You’ll need to consider how you will make up the salt water for your tank – bags of salt can be purchased from aquarist shops. Do you have transport to collect the heavy bags on a regular basis?
  • Where is your nearest aquarist shop – time and transport costs can add up if you don’t live near a good aquarist shop.

Should you Find Dory??

After the release of Finding Nemo in 2003, the sales of clownfish skyrocketed. Clownfish easily breed in captivity, yet to match the high demand, over 90% of clownfish that were sold were collected from the wild. This resulted in the extinction of local populations on certain coral reefs.With the release of Finding Dory there are many fears that the same will happen to Regal Tangs. Even more worrying is that Regal Tangs rarely breed in captivity and so a much higher percentage will have to be wild caught, potentially destroying wild populations.We strongly recommend that you do not set up a marine tank to keep Regal Tangs. They can grow to at least 30 cm in length and are highly sociable. Providing a big enough tank to keep them happy and healthy will be very difficult.

If you want to see real live Regal Tangs, come to visit our new display at the National Marine Aquarium. Your Day Plus Pass ticket will allow you access to these beautiful fish nearly everyday for FREE after your initial purchase of the ticket.


We look forward to seeing you!!

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