Microfauna
Microfauna refers to the small, often microscopic invertebrates, such as copepods, amphipods, and various worms, that naturally inhabit a reef tank’s live rock, sand bed, and refugium. These organisms play an important supporting role in a healthy reef ecosystem, helping process detritus, contributing to the broader nutrient cycle, and serving as a valuable natural food source for fish and certain corals.
A thriving microfauna population is often considered a sign of a mature, biologically balanced tank, since these organisms generally require stable, undisturbed conditions to establish and reproduce successfully.
Why It’s Important
- Helps process detritus and organic debris as part of the broader nutrient cycle.
- Serves as a valuable natural food source for fish, corals, and other predators.
- Indicates a mature, biologically balanced reef tank when populations are thriving.
- Supports biodiversity throughout the rock, sand, and refugium environments.
How It Works
Microfauna populations establish naturally over time on live rock and sand, or can be introduced more deliberately through starter cultures, gradually reproducing and expanding as conditions allow. Refugiums are particularly valuable for supporting microfauna, since their protection from display tank predators allows populations to grow far more successfully than in open display conditions.
As microfauna populations mature, some individuals migrate or are swept into the display tank, providing a small but consistent natural food source for fish and certain planktivorous corals, supplementing whatever direct feeding a reef keeper provides.
Microfauna and Related Concepts
Microfauna is closely tied to copepods and amphipods, its most commonly discussed representatives, and to refugiums, the equipment most often used to support and cultivate healthy populations. It’s also relevant to detritus and the nitrogen cycle, since microfauna contribute meaningfully to processing organic waste.
Reef keepers hoping to boost microfauna populations often introduce starter cultures directly into a refugium, then avoid excessive predation pressure or overly aggressive maintenance in that space to give populations time to establish and reproduce. Patience is generally rewarded, since healthy microfauna populations tend to become self-sustaining once established.
Reef keepers can support microfauna populations further by avoiding excessive vacuuming of the sand bed and minimizing the use of broad-spectrum medications that might otherwise harm beneficial invertebrates alongside any target pest. Introducing multiple starter cultures over time, rather than a single batch, can also help build a more diverse and resilient microfauna population capable of supporting a wider range of predators and contributing more effectively to the tank’s overall detritus processing capacity.
Common Misconception
A common misconception is that microfauna populations are unimportant compared to more visible tank inhabitants like fish and corals. In reality, they perform essential, ongoing ecological functions, and their presence or absence can meaningfully affect a tank’s overall biological balance and nutrient cycling.
The Bottom Line
Microfauna are the small invertebrates inhabiting a reef tank’s rock, sand, and refugium, supporting detritus processing and serving as a natural food source. Thriving populations are a positive sign of a mature, well-balanced reef ecosystem.
