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A saltwater aquarium is often the pinnacle of every fish keepers’ dreams. The fascinating array of colours and behaviours, coupled with unique invertebrates and corals, can create a beautiful showpiece in any home. Marine aquariums are often accompanied with the preconception that they are harder to keep than freshwater setups. While marine fish are a little less tolerant of poor water quality, the same basic principles of care and maintenance apply to both.


Choosing the Marine Aquarium - Size, Shape & Positioning

Marine aquariums can come in an array of shapes and sizes. A trip to your local specialist marine retailer will give you the chance to see the latest aquariums the hobby has to offer. A traditional marine setup would consist of an aquarium on a cabinet containing another aquarium inside (the sump filter). This modular filtration system suits marines as it allows most of the equipment to be hidden underneath the main aquarium. The water will drain from the main tank via gravity and return using a pump in the last chamber of the sump.  Other options are available, including aquaria where filtration, heating and skimming are incorporated into the back of the aquarium.

A marine aquarium of about 120 litres or more is the preferred minimum. This allows for a greater choice in livestock and helps prevent dangerous fluctuations in water chemistry. The larger the aquarium size, the greater volume of water it can hold. Smaller aquariums are certainly achievable, but water quality parameters are more likely to experience larger fluctuations. This variability of water quality can often lead to stress which weakens the immune system increasing the chances of disease taking hold. It is therefore recommended to buy an aquarium as large as one can afford and ca fit in the home. Any hobby should be within the hobbyist’s budget, and with the great variety of aquariums on offer there is usually something for everybody.

The placement of the aquarium in the home should also have some thought. An aquarium should not be positioned:

  • In direct sunlight (which can cause nuisance algae)
  • In an area with high footfall (excessive vibration can stress fish)
  • In a room with a high variability in temperature, such as a conservatory
  • Near a radiator
  • Near a speaker or sound system

Aquariums should always be level to prevent any stress on the glass. Also consider the weight of the aquarium once it's filled with water, substrate and rock. Saltwater is also heavier than freshwater due to the salt content. A 200-litre aquarium, including gravel, water, salt and the glass could weigh in excess of 300 kg (47 stone)!  Always make sure that the supporting surface can handle the weight, if in doubt consult with a structural engineer.

Marine Life Support Equipment

Much of the fundamental equipment needed to maintain a saltwater aquarium is the same as freshwater. Due to the sheer volume of water, the natural marine habitats where our favourite marine fish are found are typically very stable environments.  Because of this, these fish have evolved to live in these stable environments and poorly adapt to significant change. This is why it’s so important to ensure that filtration and temperatures remain as optimal and stable as possible.

Aquarium filters utilise up to three different styles of filtration - mechanical, biological and chemical. To achieve the best filtration, marine aquariums rely on all three.

Mechanical Filtration is the physical removal of waste from the water. This is usually achieved by using filter socks or foams that trap dirt in the water column. These can then be rinsed off (in aquarium water) and replaced.

Protein skimmers are a piece of specialist equipment used in marine aquariums. These skimmers remove organic compounds from the water by using protein’s natural affinity for the surface area of bubbles. Bubbles are injected into a cone-like structure, the proteins and other organic materials stick to the bubbles, rise up the column, and overflow into a collection cup. . This ‘physical removal’ of organics makes it a mechanical filter, of sorts.

Biological Filtration utilises friendly bacteria to breakdown toxic ammonia into less harmful nitrite and nitrate. There is usually biological media in the sump filter, which has a very large surface area to maximise bacterial colonisation. Filter media can be sponge, sintered glass / ceramic media or fluidised plastic media. Live rock inside the main aquarium also acts as biological filtration. When enough water flow is circulated around the tank, the porous structure of live rock allows it to be colonised by bacteria. Some marine setups bypass biological filtration altogether and rely on the live rock to perform that function.

Refugiums can also be classed as biological filtration. These are partitions, often inside the sump, that provide an ideal environment to grow marine algae and invertebrates. Growing and harvesting marine algae is a natural way of reducing nitrate and phosphate from the water.

Chemical Filtration is the absorption of compounds using specialist filter media. The typical chemicals that can be removed from water using chemical filtration include phosphate, odours, colours and other organic compounds. Phosphate is the primary target for chemical filtration in marine aquariums as excessive amounts encourage nuisance algae growth and inhibit healthy coral growth.

Our Marine Phosphate Remover has a very high affinity for phosphate, does not clump nor re-release phosphate back into the water.  This product can be used in conjunction with Marine Anti-Phos that converts phosphate into a solid which is then removed via mechanical filtration.

Marine aquariums also require other electrical items to ensure the survival of its inhabitants. Most saltwater tanks will need a heater as the majority of species offered for sale are from tropical climates. Remembering that seas and oceans do not fluctuate much in temperature, it may also be necessary to install a chiller to ensure the temperature does not increase too much in the summer months, especially if you are looking to keep a good selection of corals which are even less tolerant of temperature fluctuations than fish. An alternative to a chiller would be to ensure the room the aquarium is in is temperature regulated (e.g. air conditioned).

Pumps are also a necessary piece of marine equipment and there are a few types available. Return pumps are used in sump filters to return the water to the main aquarium. The flow rate of the return pump should be 5 to 10-times the volume of the entire aquarium volume (tank & sump). For example, if the aquarium was 200 L and the sump 80 L, the flow rate of the return pump should be 1400 L/hr - 2800 L/hr. Generally, it is recommended to aim towards the higher end to account for flow loss in pipework and head height.

The other style of pumps used are circulation pumps. These usually have very high flow rates for their size and wattage, in comparison to return pumps. Their wide-angle outlet is also designed to reduce pressure without reducing flow. To calculate the correct size circulation pump, it should be x20 times the aquarium volume. For example, a 200 L tank would need a 4000 L/hr circulation pump. This can be a single pump of 4000 L/hr,or ideally made up of several smaller pumps connected to a programmable control box to create optimal circulation and reduce ‘dead spots’, this is especially true if you have a large amount of rock in the aquarium

Hardscape & Substrate

One of the most anticipated parts of setting up a new marine aquarium is decorating the main tank. There are many different ways to achieve a natural look, using a variety of substrates and rocks. Many products will be advertised as ‘live’. This term implies that the substrate, be it coral sand through to ocean rock, is colonised with microorganisms, such as those responsible for biological filtration. Using live substrates  will help to speed up the maturation process of the nitrogen cycle. A cheaper alternative is to use coral sand or gravel, and over time, this too will colonise with bacteria.  In both cases the process can be boosted by the addition of Marine Live Filter Bacteria.

Rocks create the structures inside the aquarium. Traditionally, ‘live rock’ was the choice of many hobbyists due again to the beneficial bacteria present in the rock that had been harvested from the oceans. In recent years, artificial live rock has grown in popularity, whilst tougher regulations on taking live rock from the wild has made it the environmentally-conscientious choice. Artificial live rock has all the benefits of real live rock (biological filtration, beneficial bacteria, porous structures) without ruining natural reefs and reducing the risk of hitchhiking pests.  If you do decide to go down the live rock route, make sure you purchase from a reputable source who sources their rock from a sustainable source.There are many different grades of live rock from base rock through to Fiji rock, and you can also purchase the rock cured or uncured*. Try to purchase the best your budget will allow as this will pay dividends in the future when the rock matures and the corals seeded in the rock start to emerge.

*Live rock is actually shipped dry due to the weight, as the rock is out of water for 24-48 hours, a lot of the life on it will die off, this is known as uncured live rock. Uncured rock will have a strong smell of ammonia and should never be added to an established set-up as it will cause an ammonia spike. This uncured rock needs to be cured in marine water with a high flow over for it for around 6 weeks, this gives the rock a chance to recover and life (including all the beneficial bacteria) to start to re-grow.

To read part two of this series, click here.

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