Keeping marine fish: Is it really as difficult as it seems?

Up until perhaps ten years ago, keeping marine fish at home was seen as the domain of experts, with very few laypeople able to maintain a healthy and thriving marine aquarium long term. Advances in technology and tank equipment now mean many hobbyists successfully keep vibrant marine tanks, though marine fishkeeping does require significant preparation and commitment.

Marine aquariums demand considerable research before you set up a tank. Understanding the unique ecosystem, tank preparation, and ongoing care will likely take weeks or months to grasp before adding fish. Many enthusiasts even wait several months between setting up the tank and introducing livestock to establish a stable environment.

Different types of marine aquariums

Marine life includes millions of species, but not all are compatible together. The fish, invertebrates, and other creatures you select must be carefully chosen to coexist and thrive. Some species are inherently more challenging to keep.

Eye-catching tanks often contain a mix of colourful anemones and corals, adding lush vibrant colours. However, anemones and corals are notoriously difficult to maintain. Dead or unhealthy anemones and corals can rapidly release toxins that jeopardise the entire tank's health.

Marine aquariums broadly fall into two categories: coral and anemone tanks, and fish-only tanks. While keeping fish alone is challenging, it is generally easier for beginners compared to maintaining delicate and complex coral systems. Some striking marine fish cannot be kept with corals as they feed on them, making fish-only tanks an attractive option to maximise species variety.

The size of your tank

Marine tanks come in a broad range of sizes, from compact setups holding just a few gallons to large bespoke tanks occupying an entire wall. Larger tanks provide a more stable environment, less vulnerable to sudden parameter swings or mistakes. This makes them more forgiving in terms of maintenance and can support a wider range of species.

While small ready-made units such as the marine BiOrb may appeal for convenience, they restrict fish and livestock numbers. Generally, purchasing the largest tank affordable and suitable for your space is advisable. Always avoid overstocking to protect animal welfare and water quality.

Is it expensive to keep marine fish?

Marine fishkeeping is significantly more expensive and time-intensive than freshwater fishkeeping. Setting up a tank with all necessary equipment can cost well over £1,000 even for a small system, excluding the cost of live animals. Marine fish tend to be pricier and specialized care adds to ongoing costs.

For those without a considerable time and financial commitment, marine fishkeeping may not be suitable.

What equipment do you need to keep marine fish?

Marine fish require a very different setup compared to freshwater. The exact equipment depends on the species and livestock you plan to keep, so knowing your intended stock in advance is critical. Here is a typical list for a beginner's marine aquarium:

• A sturdy tank designed for saltwater use
• A cabinet or stand with space for specialised filtration equipment
• Heater and thermometer to maintain temperature stability
• A sump — a secondary tank below the main to help filter water
• Protein skimmer to remove organic waste and pollutants (note some skimmers can be noisy)
• Multiple power heads to ensure healthy water movement
• Live rock containing beneficial bacteria and microorganisms for biological filtration
• Live sand substrate for natural filtering
• High-intensity lighting tailored to the plants or corals intended
• Hydrometer or refractometer to measure salinity accurately
• Water testing kits, supplements and additives
• Essential tools like nets, siphons, buckets, and tubing
• A supply of saltwater, either commercially prepared or created using reverse osmosis filtered tap water and marine salt mix

Sustainability and responsible purchasing

Almost all marine fish and invertebrates are wild-caught rather than bred commercially in captivity. Ethical sourcing is crucial to protect delicate ocean ecosystems and preserve stocks.

Buy your marine livestock from suppliers who can verify provenance, explain how fish are caught, and show sustainable practices. For example, live rock should be collected responsibly, ideally from dead or broken reef material rather than from healthy coral reefs.

Further information

Interested in learning more about keeping marine fish? Below are helpful external resources offering advice and community support:

Practical Fishkeeping
Ultimate Reef Forum

Summary and final tips

Keeping marine fish is more demanding and costly than freshwater, but it is not beyond the reach of dedicated hobbyists. The keys to success include thorough research, choosing appropriate equipment and livestock, maintaining stable water conditions, and sourcing animals ethically.

Start simple, be patient as your tank cycles and matures, and keep learning. With care and commitment, a beautiful marine aquarium can be a stunning and rewarding feature in your home.

For those considering fish-only marine tanks, remember the broader choice of species available and slightly easier maintenance. For coral or anemone tanks, be prepared for a steeper learning curve, higher costs, and greater attention to detail for animal welfare.

Ensuring you are fully informed and prepared before setting up your tank will help provide a safe, healthy environment for your marine fish and other aquatic life for years to come.

For finding marine fish and aquarium equipment in the UK, looking to find marine fish for sale at reputable retailers can be a great place to start.