Marine aquarium — coral reef (reef)

1 topic in this section

Overall difficulty: ★★★☆☆ (soft corals and LPS) to ★★★★★ (predominantly SPS) Setup cost: very high Recommended minimum size: 150 L (soft corals/LPS) / 300 L (SPS) Who it's for: advanced – expert

Description

The most demanding, most expensive, and most spectacular aquarium in the entire hobby. Live corals take center stage. It requires a perfect balance of light, water flow, water chemistry, and parameters that mimic the natural ocean. The reward is an underwater ecosystem of extraordinary beauty.

Water Parameters (NSW — Natural Seawater)

Parameter	Soft/LPS	Mixed LPS/SPS	Dominant SPS
Temperature	23-27°C	25-26°C	25-26°C (±0.5°C)
pH	8.1-8.4	8.2-8.4	8.2-8.4
Salinity	1.023-1.026	1.024-1.026	1.025-1.026
Ca	350+ ppm	400–430 ppm	420–450 ppm
KH (Alk)	7–11 dKH	8–10 dKH	8–9 dKH
Mg	1,200+ ppm	1,250–1,350 ppm	1,300–1,400 ppm
NO3	< 20 ppm	< 5 ppm	2–5 ppm
PO4	< 0.1 ppm	< 0.05 ppm	0.03–0.05 ppm

Essential Reef Equipment

Equipment	Purpose
High-quality skimmer (Nyos, Deltec, Bubble Magus)	Remove organic matter before it decomposes
High-flow circulation pumps (Tunze, Jebao)	Water flow for corals (20–40 times the volume per hour)
High-quality LED/T5 lighting (Radion, AI Hydra, Kessil)	Photosynthesis in zooxanthellae; precise PAR
Sump + shelter with macroalgae	Filtration, stability, copepods
ATO (Auto Top Off)	Automatically replenish evaporation
Dosing Pump + Balling System (GHL, Kamoer)	Precisely and automatically replenish Ca, KH, and Mg
Reef controller (Apex, GHL)	Comprehensive Monitoring and Automation
High-Quality Refractometer (ATC)	Daily Salinity
Complete test kits (Hanna Colorimeter, Salifert)	Weekly testing of Ca, KH, Mg, NO3, and PO4

Common Algae — What They Are, Why They Appear, and How to Get Rid of Them

On the reef, algae are one of the biggest challenges and one of the most accurate indicators of the system's health.

Establishment Phase (first 8–16 weeks)

Every new reef goes through phases of algae growth before it stabilizes. This is normal and necessary.

Weeks 1–4: Diatoms A brown film over everything. Normal. Nassarius and Trochus keep it under control. It goes away on its own.

Weeks 4–8: GHA (Green Hair Algae) Green patches on rocks and glass. A sign that NO3 and PO4 levels from the initial cycle are high.

Improving the skimmer
Cleanup crew: Trochus, Nassarius, hermit crabs, emerald crab
Algae-removing blades

Weeks 6–12: Dinoflagellates (Dinos) The most feared enemy of the new reef. Sticky brownish-yellow slime on the sand. (See the full protocol section below)

Weeks 12–24: Coralina Algae (CCA) The appearance of pinkish-purple CCA on the rocks means that the reef is establishing itself properly. Welcome.

Bryopsis (Green Featherweed)

Appearance: Green filamentous algae with feather-like branches, 2–8 cm long. Very difficult to remove. Why: It appears when other controls fail; it is resistant to most treatments. Solution:

Fluconazole (antifungal): the only proven treatment. Precise dosage in circulating water. May affect invertebrates; use with caution and proper preparation.
Labros (Halichoeres, Pseudocheilinus hexataenia): They eat some Bryopsis
Thorough manual removal

Cyanobacteria (Red Marine Cyanobacteria)

Why in a reef tank: High NO3, unbalanced PO4, poor circulation. Solution:

Improve circulation (Gyre pumps are excellent for eliminating dead zones)
Reduce food intake
Active macroalgae shelter (absorbs NO3 and PO4)
More Frequent Water Changes

Dinoflagellates (Dinos) — The biggest problem facing the reef

Appearance: Viscous brownish-yellow mucus, sometimes with bubbles. It appears at night or in the early morning and partially dissolves in daylight. It covers the sand and the bases of the corals. Why: Multiple causes: a new system with no established competition; very low NO3 and PO4 levels (paradoxical); water that is "too clean" and lacks a diverse bacterial population. Complete disposal protocol:

Identify the type of dino (microscopic if possible: Ostreopsis and Amphidinium are the most toxic)
Increase NO3 to 5–10 ppm and PO4 to 0.05–0.1 ppm if they are very low
Total darkness for 3–5 days (cover the aquarium completely)
Physically use a siphon to remove debris every morning before turning on the light
Inoculating copepods and amphipods (Tisbe, Tigriopus): biological competition
Increase bottom circulation (dinosaurs are benthic)
Patience: It may take 6–12 weeks to fully get under control

"New Tank Syndrome" in marine life

The first 6–12 months of a reef tank are the most unstable. It’s normal to experience algae blooms, fluctuations in water parameters, and difficulties getting the tank established. Patience is the most important virtue when it comes to reef tanks.

Most Common Mistakes

Add corals before the system is stabilized (at least 3–6 months for LPS; 12+ months for SPS)
Do not quarantine the fish (this introduces ich, which spreads throughout the entire system)
Do not add Ca/KH/Mg when the corals' consumption exceeds the amount removed during water changes
Unstable parameters (worse than slightly low but stable parameters)
Skimmer is insufficient for the system's volume

Key Tips

The stability of the parameters is more important than their exact values
Start with soft corals and easy LPS (Zoanthus, Mushrooms, Hammers) before trying SPS
A refuge with Chaetomorpha or Caulerpa taxifolia is the best natural method for reducing NO3 and PO4
Always have seawater on hand for emergency water changes
Record all parameters weekly to identify trends before they cause problems