How to: Set up & maintain a marine aquarium

Keeping an aquarium at home can be an enjoyable and rewarding hobby for both adults and children. It’s been shown that a healthy and well maintained aquarium can reduce your stress levels. Marine aquaria can add fascinating colours and a wide range of organisms to your home. However, before purchasing an aquarium, you should consider all the aspects raised on this page to ensure that the underwater community you choose to create is looked after properly and that the fish remain healthy. As a general rule you should buy an aquarium as big as possible. Larger aquaria contain more water and are easier to maintain a healthy environment for your fish.

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See below for our top tips.


Before you buy your fish make sure:
• You’ve the correct equipment and position for the aquarium
• You’ve researched all the species you are interested in and
your final choices are all compatible to live together
• You’re familiar with how to transport and release your fish
• You’re aware of the daily, weekly and monthly maintenance
your aquarium will need
• You’re prepared to look after your fish properly for the
duration of their life


The equipment required for a marine set-up is more advanced
than that of a freshwater one. Below is a preliminary list of

Initial requirements:
• Glass/acrylic aquarium and suitable stand
(It is easier to maintain good water quality in larger tanks)
• Marine aquarium salt and bucket for mixing
• Filter
• Marine gravel/sand
• Live rock
• Thermometer
• Hydrometer
• Heater
• Gravel cleaner
• Water testing kits
• Food

Additional useful equipment:
• Protein skimmer and power heads
• UV steriliser
• Advanced lighting systems (especially for a reef tank)
• An ozoniser
• Reverse Osmosis (RO) water filter

Positioning your tank

Once the equipment is ready, the tank should be positioned
carefully so it is:
• Out of direct sunlight and away from sources of heat
• On a perfectly flat level surface or stand which can
indefinitely support the weight of the tank when it’s filled
with water

Adding your saltwater

Before the water is added to the aquarium, specialised marine
salt for aquaria needs to be mixed with the water. A Specific
Gravity (S.G.) of 1.020-1.025 is required at between 23-28°C.
Salt water should be prepared carefully following the
manufacturer’s guidelines.

Adding your fish

There are different types of marine tank which can be
established: reef fish only and community. On the whole,
a fish-only tank is a good starting point for a newcomer
to keeping a marine aquarium. A fish-only tank can easily
be turned into a reef tank in the future as you become
more experienced, though you may need to buy additional
equipment. Remember, if you do keep any invertebrates,
remember you should never use copper treatments as these will
kill them.

Always seek advice before purchasing fish - not all species
are compatible to live together. Some have specialised
requirements and others may become aggressive with age.
Add fish slowly. Overstocking or stocking too quickly may
cause ‘new tank syndrome’ where the filter is not capable of
coping with the increased waste load. The water quality can
quickly deteriorate to unhealthy levels and sometimes fish will
not survive.

Be aware of what a healthy fish looks like - healthy fish have
clear bright eyes, undamaged fins, intact scales, no ulcerations
or bumps, appropriate swimming and steady breathing. Do
not purchase a seemingly healthy fish if sickly fish are present
in the tank with it, as fish can carry diseases without showing

Stocking levels

It is not possible to say exactly how many fish your aquarium
can hold - marine fish are often territorial, so one fish may
claim large areas of the tank, displaying aggressive behaviour to
others in the tank. This can sometimes be reduced by moving
around the rock and décor display.

Please check the compatibility of your fish and invertebrates
with our Aquatics Team. Some species may start out small but
turn out to be far too big for your aquarium. There are several
marine fish which are poisonous so be sure to research the
species or ask for advice before purchase.
Do not expect to fill your tanks with as many fish as the stores
do, they are able to do this due to expertise and advanced
filtration systems.

Some species require bright lighting, others fast water flow.
Ask our colleagues for advice, it is often simple to adapt your
aquarium for species’ requirements. The closer the aquarium
mimics the natural environment, the healthier the fish will be.

Never release your aquarium animals or plants into the wild

Never release an animal or plant bought for a home aquarium
into the wild. It is illegal and for most fish species this will lead
to an untimely and possibly lingering death because they are
not native to this country. Any animals or plants that do survive
might be harmful to the environment.