What to buy, how to set up, and what to stock in nano reef tanks (5-30 gallon). Equipment lists, sizing rules, stocking ideas, and the most common mistakes.
Nano reef tanks (5-30 gallon) are the entry point for most modern reef-keepers. They are cheaper to start, faster to fill with coral diversity, and forgiving of equipment shortcuts that would crash a larger system. The trade-off is parameter swing: smaller water volumes mean smaller mistakes hit harder. The right candidate for a nano reef has 30 minutes a week for water testing + parameter checks, $1000-2500 for a starter build, and the patience to add livestock slowly over the first 6 months while the system matures.
Core stack: a 10-30 gallon all-in-one (AIO) tank like an Innovative Marine, Waterbox, or Coralife Cube; a quality LED (Kessil A80, AI Prime 16HD, NICREW HyperReef); an internal protein skimmer or HOB skimmer; a 50-100W heater with controller backup; a refractometer; salt mix; RO/DI water (jugged from your LFS or a small countertop unit). Optional but recommended: an ATO, a small wave maker (MP10 or Sicce equivalent), and a basic doser for two-part as the coral load grows.
Light: target 250-400 PAR at frag-rack height for mixed reef. Most quality nano LEDs hit this at 60-80% intensity. Filter: AIO chambers with filter floss + carbon + GFO + skimmer or chaeto refugium. Turn over the display 5-8x per hour with a small wave maker.
Honest nano stocking: 1-3 small fish (clown goby, neon goby, ocellaris pair if 20+ gal); a small CUC of hermits + snails; 6-15 coral frags spanning softie / LPS / one or two beginner SPS like montipora. Browse saltwater fish, coral, and marine inverts filtered to nano-compatible species on Fast Aquatics.
Most-common mistake: rushing the cycle. New nanos that get coral or fish in the first 4 weeks crash on ammonia/nitrite spikes. Cycle for 6-8 weeks with bottled bacteria + liquid ammonia, test until both ammonia and nitrite read 0 within 24 hours of dosing 2 ppm ammonia, then add livestock slowly.
$700-2,500 for a complete nano build (tank + light + skimmer + heater + powerhead + ATO + RO/DI + salt + livestock starter). Coral frag collection grows from there at $20-150 per frag depending on rarity.
Yes if you respect the parameter-stability trade-off. A nano reef demands weekly testing but rewards aquarists who care about the details.
A backup heater. Single-point-of-failure on heaters is the #1 cause of reef-tank disasters. Run two undersized heaters with a controller instead of one full-sized.
4-8 weeks. Test ammonia + nitrite daily; both must read 0 within 24 hours of dosing 2 ppm ammonia before adding fish.
Saltwater to freshwater is straightforward (drain, scrub, refill). Freshwater to saltwater means stripping all hardscape and replacing rock + sand with marine equivalents.