Marine aquariums are one of the most impressive types of tanks, but they are more complex than freshwater or tropical setups. Marine fish and corals require specific water conditions and equipment, so preparation and research are key. Here’s a step-by-step guide for setting up your first marine aquarium.

Equipment You’ll Need:

  • Aquarium and stand

  • Lighting and timer

  • Sand and live rock

  • Filter and protein skimmer

  • Heater and thermometer

  • Powerheads or pumps

  • Test kits and saltwater mix

  • Fish food and net

  • Aquarium vacuum and scrubber

  • Quarantine tank

  • Rubber gloves and power strip

Aquarium Location:

Choose a stable location away from windows, radiators, or direct sunlight. Ensure the stand can support the full tank weight: roughly 10 pounds per gallon plus equipment, live rock, and livestock.

Setting Up Your Tank:

  1. Rinse the aquarium with freshwater only; avoid soap or detergents.

  2. Install the heater, filter, protein skimmer, and other equipment—but don’t plug them in yet.

  3. Add a background to reduce fish stress.

Preparing Saltwater:

  1. Mix saltwater in a 5-gallon bucket following the salt mix instructions.

  2. Use a hydrometer or refractometer to achieve a specific gravity of 1.021–1.024.

  3. Pour the saltwater into the tank and circulate for a few days before adding livestock.

Live Rock:

  1. Place live rock in the tank and aim powerheads toward it.

  2. Scrub dead debris with a soft brush every few days and siphon out waste.

  3. Monitor water parameters to ensure the tank is cycling properly.

Substrate:

  1. Premix 2 gallons of saltwater in a bucket, add sand, and stir to remove dust.

  2. Add sand to the tank carefully, avoiding live rock.

  3. Blow off excess sand with a powerhead and let the tank settle for a few days.

Water Parameters Before Adding Fish:

  • Temperature: 24–27°C (75–80°F)

  • Specific gravity: 1.020–1.024

  • pH: 8.0–8.4

  • Ammonia: 0 ppm

  • Nitrite: 0 ppm

  • Nitrate: ≤20 ppm

  • Carbonate hardness: 7–10 dKH

Converting a Tropical Tank to Marine:

Many freshwater tanks are suitable for marine setups, but check for:

  • Exposed metal screws (may corrode)

  • Non-waterproof lighting

  • Silicone discoloration (copper leaching can be toxic to corals)

Substrate and Filtration:

  • Use sand or crushed coral for marine tanks. Live sand helps start biological filtration.

  • Ensure your filter can handle marine bioload; protein skimmers are essential.

  • Internal or external filters work, but marine tanks often require stronger filtration.

Lighting and Pumps:

  • Freshwater lights are fine initially, but actinic blue lights are better for corals.

  • Pumps or powerheads create water movement necessary for marine fish health.

Decorations and Heaters:

  • Artificial rocks, coral, and stones from freshwater tanks are safe. Avoid plastic plants.

  • Most heaters work for marine tanks; check specifications.

Water Testing:

  • Freshwater test kits are insufficient. Marine tanks require specific tests for salinity, alkalinity, ammonia, nitrite, and nitrate.

  • Use a refractometer to monitor salt levels (ideal marine range: 1.024–1.026 ppt).

Fluidised Bed Reactors:

  • Used for biological filtration, circulating water through sand or pellets.

  • Minimal maintenance, but the pump and bed should be checked regularly.

Brackish Aquariums:

  • Brackish tanks are between freshwater and marine in salinity.

  • Fish are adaptable, but water salinity and pH should be monitored for a stable environment.