Many people are coming to realize that it is possible to maintain a reef successfully in tanks smaller than twenty gallons. Unfortunately, there is often an assumption that these tiny reefs are cheap and easy to keep.  It is vital to realise that this is not always the case, especially for beginners. 

Nano reefs are by their very nature small, which means that they are prone to rapid environmental fluctuations (e.g. temperature and salinity).  On the other hand, the oceans are a very big and environmental variations happen very slowly.  This means that most marine fish and invertebrates are simply unable to cope with rapid changes, having never had the need to.

In short a nano reef is very unforgiving of mistakes, even the best nano reef doesn't have the inherent stability and buffering that a larger aquarium has.

The Three "Golden Rules"

1/ Livestock: it's a small tank so it needs small livestock

Things to avoid:

*Its a small tank so nothing too big!

*Anything that releases toxins, e.g./ sea apples a nano tank is just too small to dilute it

*Anything that grows really fast, like Caulerpa as it can over run a nano tank in fairly short order

Fish

Most small non-territorial fish are excellent choices for a nano reef. A maximum size of approx 3" is best.  We would not recommend any fish for a tank volume of less than 5 gallons.  Tanks of this very small size are more suited to invertebrates.

Ideal choices would be the various clownfish, pygmy cherub angelfish, gobies, blennies, the more gentle damsels and pseudochromis.

Soft Corals

Pretty much all the easy soft corals do well in Nano Reefs, although some need frequent thinning out.

Colt Coral, Pulsing Xenia, Devils Hand, Encrusting Gorgonians,  Mushroom Anemones, Ricordia, Zooanthus

It should be noted that many soft corals release chemicals which adversely affect hard corals, in such small aquariums this can make it wise to keep either one or the other.

Hard Corals

SPS Corals like Acropora - small cuttings of about an inch,

Small colonies of Favites, Closed Brain Coral, Hammer Coral, Torch Coral, etc

Molluscs

Tridacna crocea and Tridacna maxima (well illuminated nano reefs only)

Turbo snails, cerith snails, nassarius snails make brilliant algae and detritus eaters.

Crustaceans

Small detritus eating hermit crabs are ideal e.g. Red Leg Hermits but they should only be stocked in small numbers, roughly one per 3 gals for the larger crabs and one per gallon for the smaller species like blue legs.

2/ Feeding: Feed only the amount your livestock will eat

Uneaten food rotting away in the substrate is a bad idea in a large aquarium and a fatal one in a nano reef.  With plankton and coral food suspensions feed only 1/3 of the manufacturers normal dose rate in a nano reef.

3/ Water changes and supplements: Always perform water changes on time and be careful with supplements

Due to their small size and relatively simple filter systems it is wise to dose nano reefs with supplements only very carefully.  In order to keep the water parameters as constant as possible it is a good idea to divide the doses of weekly supplements into a daily equivalent e.g. instead of adding say 7ml of calcium once a week add 1 ml a day. Often a 20% weekly water change will remove the need for supplementation.