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Marine Nano Reef

Marine Nano Reef Set Up Guide and Care Sheet

Developed with and approved by a qualified veterinarian.

Nano Reef Aquarium


If you are looking to bring a slice of a coral reef into your home but are limited on space, a nano marine aquarium might be the right choice for you. Nano reef aquariums are small yet intricate systems filled with a variety of aquatic life, mainly corals. The term nano typically refers to a tank size that is under 20 gallons. A little extra care and patience in the beginning will go a long way toward creating a healthy marine aquarium for years to come. Appropriate fish species for a nano reef can be limited, so do your research to determine the best fit for your aquarium.

Table of Contents


Habitat size

Although nano reefs are small aquariums by definition, it is always recommended you choose the largest aquarium you can because water conditions can change rapidly in smaller water volumes.


Before doing any work with the aquarium itself, determine the best location for it. It should be placed away from direct sunlight, windows, outside doors, heat vents and air conditioners. Rapid changes in water temperatures are extremely stressful for all fish—and especially for marine life.

Keep in mind that once it's set up, your tank will weigh approximately 8 pounds per gallon that it holds. That means a 10-gallon tank will weigh over 80 pounds! Be sure your floor will support this amount of weight, and a stand is used to ensure the tank is stable and level. If you rent your home, be sure to check your lease. Some apartments and condos limit the size of aquariums allowed. Also, check for electrical outlets. Most marine aquariums will need access to at least four sockets.

The use of live rock and sand is highly recommended to kickstart the nitrogen cycle in your tank. Live rock and live sand are not technically alive. “Live” refers to the bacteria, algae, sponges, crustaceans, and other invertebrates who live on and within the rock and sand. Using these live components will effectively shorten your tank’s cycling period.

Initial setup

Start by rinsing out the tank with warm water to get rid of any dust or debris inside.

Position the aquarium stand into place, adjusting to make sure it's level. If you don't have access to a carpenter's level, place the tank on the stand and fill with one to two inches of water. Check to see that the water is an even distance from the top of the stand on all four sides; an unbalanced aquarium can be extremely hazardous. Placing a tank on an uneven or tilted surface increases the risk that the tank will tip over, crack or leak. A proper stand designed for an aquarium is important; using anything other than a manufactured tank stand may void your tank's warranty.

Make sure there is enough space between the wall and the back of the aquarium to adequately fit filters, cords and to allow easy access for maintenance.

If using an aquarium background, affix the background to the tank prior to filling with water and placing the aquarium against the wall.

Fill the tank approximately 1/3 full. Carefully dry off the bottom edge of the tank and stand. Now check for leaks. Look for water beading up on the bottom edge or running down the sides of the stand. If the tank leaks, empty it and return it to the store for a replacement. You can attempt to fix it, but repairing a leaky tank is difficult, with no guarantee of success.

Filter and skimmer

Set up your filter and protein skimmer, if you choose to use one, according to the manufacturer's directions. Do not plug your filter or protein skimmer in at this time.

Add substrate

Thoroughly rinse the substrate and décor before placing it into the aquarium. (A kitchen colander works well but be sure to disinfect it before using it for food preparation.) If utilizing live sand, rinse it in a small bucket of premixed saltwater and discard the dirty saltwater after rinsing. Do not add live sand to the aquarium until after the salt has been added.

Fill the tank

If no leaks have been noted, continue to fill the tank with water, leaving a couple of inches from the top to allow for water displacement if live rock and sand are being added. To protect the décor and aquascaping, as well as to prevent splashing, place a small saucer or bowl into the tank and pour the water directly onto that. Recheck the tank for leaks.

Add the appropriate amount of water conditioner or additive to the tank.

Heater and thermometer

Place the heater into the tank, but do not plug it in yet. The best place for the heater depends on the type of heater. Non-submersible clip-on heaters that must hang vertically in the tank should be placed as close to the outflow of the filter as possible. Submersible heaters should be placed as close as possible to the inflow of the filter. These placements allow the heated water to be better dispersed throughout the tank. Recheck the aquarium again for leaks.

Install the thermometer according to the manufacturer's directions. The thermometer should be on the opposite end of the tank from the heater in a position that is easy to check. Place the hood and light (if applicable) onto the tank. Plug in the filter and light. Make sure the cords running from the tank touch the ground before looping back up to the plug. This is called a “drip loop” and prevents water from running down

the cord into your electrical socket. You may find that the tank's level drops slightly when the filter starts. Add as much water as necessary to bring the water level to the appropriate level.

Wait 20 minutes, then plug in your heater and protein skimmer. Top off your water level, if needed. Following the instructions included with the heater, adjust your heater to keep your tank between 74 and 80°F.

Adding salt, live sand and live rock

Finish by slowly adding commercial marine salt until you get a specific gravity reading of around 1.020, testing with the hydrometer or refractometer. Your goal is a specific gravity of 1.023 to 1.025 for a nano marine aquarium. It may take up to 24 hours for the specific gravity level to stabilize, so wait before making your final specific gravity adjustments. After the specific gravity has reached 1.020, you can add live sand and live rock, if utilized. Finish adding additional water to complete filling the aquarium if needed.

Stabilizing period

Your marine aquarium is now set up and running, but don't rush off to buy fish just yet. You need to wait until the temperature and specific gravity have remained stable for at least 24 to 48 hours. This allows the atmospheric gases in the water to dissipate and salt to fully dissolve, and lets you ensure your heater is working correctly. Don't be panicked if your water becomes cloudy; this is natural but wait until the cloudiness dissipates before adding fish.

If the water temperature and specific gravity levels have remained stable for at least 24–48 hours and the cloudiness has disappeared, you are now ready to begin the cycling process of your new tank. Additives can help speed up the nitrogen cycle. Please refer to the Nitrogen Cycle Care Sheet for your next steps.

Ongoing maintenance and care

Water maintenance

Maintaining great water quality with regular water changes and adequate filtration is important to help keep your marine nano reef tank healthy.

  • Daily: Check filter, water temperature and other equipment.
  • Weekly: Test water quality at least once a week. Ensure alkalinity, calcium and magnesium levels are stable. Dose additives to support the growth of coral based on testing results. Scrape algae growth as needed
  • Weekly to monthly: Change 10–25% of the total volume of water every 2–4 weeks, or as needed; change filter media monthly.

Cleaning your habitat

CAUTION: Never use soap or any chemicals on any elements of a fish tank. A 50/50 mixture of water and vinegar works very well to clean the exterior of the aquarium and any components needing a refresh. Soap and other chemicals can be harmful to aquatic life.

Tank health / troubleshooting

Issue Causes Suggested Action
Cloudy Water Tank cycling (bacteria bloom), substrate residue, organics and heavy minerals in tap water Perform a water change and siphon the substrate, removing residual debris; water clarifier additive may help; reverse osmosis can remove contaminates found in tap water; add nitrifying bacteria additive
Green water Algae bloom, too much light (direct sunlight), excessive nutrients, overfeeding, overstocked aquarium Reduce photo period and block any direct sunlight; increase water changes; reduce feeding; ultraviolet filtration can assist with destroying algae cells
pH fluctuations Buildup of organic material and debris, increased levels of CO2 Perform a 10–25% water change; reduce feeding; increase water circulation and surface agitation
Ammonia spike Insufficient nitrifying bacteria, too many fish Perform a 10–25% water change but do not siphon the substrate; reduce feeding, add a nitrifying bacteria additive.

Additional care sheets

Notes and sources

Ask a Pet Care Center associate about Petco's selection of products available for the care and happiness of your new pet. All products carry a 100% money-back guarantee.

Because all aquatic life are potential carriers of infectious diseases such as atypical mycobacterium and salmonella, always wash your hands before and after handling your aquatic life or habitat contents to help prevent the potential spread of disease.

Pregnant women, children under the age of 5, senior citizens and people with weakened immune systems should contact their physician before purchasing or caring for aquatic life and should consider not having aquatic life as a pet. Go to for more information about aquatic life and disease.

The information on this care sheet is not a substitute for veterinary care. If you need additional information, please contact your veterinarian as appropriate.