Saltwater Mixed Reef Style Guide
A mixed reef combines soft corals, large-polyp and small-polyp stony corals on live rock, requiring stable parameters, strong flow and intense lighting.
Overview
A mixed reef is a marine aquarium that houses several coral groups together - soft corals, large-polyp stony (LPS) corals and small-polyp stony (SPS) corals - on a structure of live rock. Because these groups have different light and flow preferences, a mixed reef arranges the layout into zones so that each coral type sits where its requirements are met.
Live rock and biological filtration
The primary biological filtration in a reef aquarium usually comes from live rock, which carries the bacteria that drive the nitrogen cycle. The rock may be collected near existing reefs or be aquacultured. In the mixed reef it doubles as the structural skeleton, built up with overhangs and caves that create both the aquascape and the surfaces on which corals are placed.
Coral groups and their needs
The coral groups differ in how much light and flow they tolerate. Small-polyp stony corals such as Acropora, Montipora, Porites and Pocillopora require high, turbulent flow and intense lighting. Large-polyp stony corals such as brain, bubble, elegance, cup, torch and trumpet corals need only moderate flow and light. Mushroom and polyp corals require comparatively little light.
Filtration: sump and skimmer
Mixed reefs are commonly run with a sump, an accessory tank below the display that holds heaters, return pumps and other equipment and keeps the show tank uncluttered. A protein skimmer is typically used: it introduces air into a water stream to create microbubbles, to which organic waste adheres and is then removed before it breaks down.
Water flow
Reef tanks are run with substantial water movement. A common reference point is a turnover of about ten times the aquarium volume per hour, although demanding SPS corals may need considerably more turbulent flow while LPS corals prefer gentler movement. Placing high-flow and low-flow zones deliberately is central to stocking a mixed reef.
Water parameters
Stability is essential. Radical temperature shifts should be avoided because they are particularly harmful to reef invertebrates and fish. Reported target ranges include salinity 1.022-1.025 specific gravity, pH 8.2-8.6 and calcium 400-450 ppm, with ammonia and nitrite held at 0 ppm.
Fish and stocking
A mixed reef is stocked with reef-safe fish that will not damage corals, chosen for small size and peaceful coexistence; gobies and clownfish are typical examples, alongside other reef-compatible groups. Genera commonly associated with the style include Amphiprion, Chromis, Centropyge, Zebrasoma and Pseudocheilinus. Bioload is kept balanced to protect water quality. This is an advanced, very-high-maintenance layout.