Start a Saltwater/Reef Tank

How to Start a Saltwater Aquarium

1. Overview

Saltwater aquariums showcase vibrant marine fish, invertebrates, and stunning natural rock structures. This guide explains how to set up a successful saltwater aquarium. See our page on the Nitrogen Cycle before starting this.


2. Choosing the Right Tank Size

Marine systems benefit significantly from higher volumes, as they improve stability, dilute waste, and give the fish ample swimming room.

Recommended sizes:
• Minimum: 20 gallons
• Ideal: 40–75 gallons
• Advanced or larger fish: 90+ gallons

(Nano marine tanks exist as nano freshwater tanks do, but they require much more attention and experience due to the extreme sensitivity of those ecosystems.) 


3. Essential Equipment

Saltwater setups require reliable equipment to maintain a stable marine environment:

  • Heater: Keeps temperatures between 76–80°F.
  • Filter: Sump, canister, or HOB, depending on tank size.
  • Powerheads: Provide flow and mimic natural ocean currents.
  • Lighting: Standard marine LEDs are fine for fish-only systems.
  • Refractometer: Ensures accurate salinity readings.
  • RO/DI Unit or RO/DI supply: Pure H2O free from contaminants.
  • Protein Skimmer (Optional but recommended): Removes dissolved organics and promotes oxygenation.

4. Salt, Salinity & Water Preparation

Use RO/DI water mixed with a high-quality marine salt mix. Aim for 1.023–1.026 specific gravity. Allow your saltwater to mix and heat with a heater to the proper temperature for 2-3 hours before use to ensure oxygenation and complete dissolution.


5. Live Rock and Aquascaping

Live rock provides essential biological filtration and forms the structural foundation of the tank. Use 0.5–1 pound of rock per gallon, and create caves, arches, or islands to provide fish with natural hiding places.


6. Substrate Options

Aragonite-based sand is the most popular substrate. It buffers pH, looks natural, and is compatible with marine life. Avoid freshwater gravel, as it provides no buffering or biological benefit.


7. Beginner-Friendly Saltwater Fish

Start with hardy, peaceful species that adapt well to captive life:

  • Clownfish
  • Firefish
  • Royal Gramma
  • Gobies and Blennies
  • Chromis
  • Cardinalfish


8. Adding Your First Fish

Introduce fish slowly, 1 or 2 at a time, to prevent overwhelming your filtration.


9. Routine Maintenance

Maintenance checklist:

  • Weekly 25-40% water changes
  • Clean glass with an algae magnet
  • Rinse the mechanical filtration in a bucket of tank water monthly
  • Test salinity weekly
  • Remove salt creep (the salt that gets on the edges of the tank and filter)
  • Inspect that pumps and powerheads are operational


Reef Aquariums: A Coral-Based Guide

1. What Makes a Reef Tank Different?

Reef tanks house corals, fish, and invertebrates. Corals require very stable water chemistry, strong lighting, higher flow, and balanced nutrient levels. This section covers all requirements for successful coral keeping.


2. Types of Corals

Corals fall into three major groups based on anatomy and, consequently, care difficulty:

Soft Corals (Beginner):

  • Zoanthids
  • Mushrooms
  • Leathers

LPS Corals (Intermediate):

  • Hammer, Torch, Frogspawn
  • Candy Cane
  • Duncan

SPS Corals (Advanced):

  • Acropora
  • Montipora
  • Birdsnest


3. Lighting for Reefs

Reef aquariums depend on high-quality LED lighting that supports photosynthesis. Soft corals thrive under moderate PAR, and SPS require stronger, more evenly distributed lighting. PAR is a measurement of the wavelength of light. Most reefers do not bother measuring PAR since the device is expensive, and most reef LEDs have online forums about proper settings for most corals. However, if you do have a PAR machine or borrow one from your LFS, below are the appropriate values per type of coral: 

Soft Corals: 50-150 PAR

LPS: 150-250 PAR

SPS: 250-350PAR


4. Flow Requirements

Corals rely on water movement to deliver nutrients and remove waste. Soft corals prefer low to moderate flow, while LPS and SPS often need moderate to strong, wave-like flow provided by multiple powerheads.


5. Reef-Safe Livestock

Only add species known to be coral-safe:

  • Clownfish
  • Small Gobies
  • Wrasses (reef-safe species)
  • Cardinalfish
  • Blennies

Invertebrates for reefs:

  • Snails
  • Cleaner Shrimp
  • Blood Shrimp
  • Peppermint Shrimp
  • Hermit Crabs (reef-safe types)

6. Managing Calcium, Alkalinity & Magnesium

Corals use these elements to build their skeletons. Reef tanks must be tested, and advanced ones must be replenished regularly.


General target levels:
• Alkalinity: 8–10 dKH
• Calcium: 400–450 ppm
• Magnesium: 1300–1400 ppm
TIP: Beginner-friendly reefs can often maintain these levels through weekly water changes alone.


7. Reef Tank Maintenance

Reef maintenance includes:

  • Weekly 20–40% water changes
  • Daily/weekly test and/or dosing of alkalinity, calcium, and magnesium, depending on coral demand
  • Cleaning skimmer cups and filters
  • Monthly cleaning of pumps and powerheads


8. Coral Placement & Compatibility

Corals have specific light and flow requirements. Aggressive LPS corals have sweeper tentacles that sting neighbors. Soft corals may spread rapidly and require fragging and/or removal. Plan your aquascape to give each coral proper space. Generally, the more light a coral needs, the higher in the tank it should be placed. 


9. Avoiding Common Reef Issues

Reefs can experience algae blooms, pests (Aiptasia, fireworms), coral aggression, and parameter swings. Prevent issues by dipping corals, quarantining fish, avoiding overfeeding, and maintaining nutrient stability.