Saltwater hobbyists consider marine tanks smaller than 30 gallons "nano" aquariums and consider them the most challenging aquariums to maintain. These small tanks have virtually no room for error. Such tanks require knowledge, diligence and top-of-the-line equipment.
Select The Best Equipment
You will want to select the highest-quality equipment for your 5-gallon tank. Additionally, you will want to use equipment rated for much larger aquariums. Bigger is better. For example, a five to ten gallon aquarium should use a protein skimmer designed for a hundred-gallon fish tank. Use powerful lighting, like T5 or LED banks. You may need a cooling fan for your lighting, since small tanks heat up quickly. You will also need high-quality live rock, preferably cured, and a good mechanical filter. You should consider setting up a sump filter, so you can attach equipment like skimmers and filter outside of the main aquarium.
Take care when setting up your nano aquarium. Use only reverse osmosis or distilled water mixed with synthetic sea salt. Shoot for a pH of 8.3, a temperature between 76 and 84 degrees Fahrenheit and a specific gravity of 1.025. Put your substrate in place and monitor the conditions daily. After the four week mark, you can add you live rock. Add it all at once. Keep monitoring the water, and if the ammonia and nitrite levels stay at zero, you can set up your skimmer at week ten. Once your skimmer is up and running, you can add your fish.
You need to take special care when adding animals to your nano aquarium. Select only small species, like clownfish, blennies and gobies. Only add one or two fish at a time, and avoid overstocking. Take care when adding corals and invertebrates as well. Add only small colonies and fragments or frags, and allow them to grow to size.
Nano tanks take more exacting care than other aquariums. Monitor all parameters closely, and pay special attention to calcium, pH and nitrate. These parameters tend to go wrong first, and have devastating effects on the aquarium inhabitants. Change about 10 percent to 15 percent of the water weekly, and add calcium as needed. In a nano tank, you must be vigilant, since any problem will become a crisis quickly.