Marine Fish & Reef Aquariums

Marine aquariums bring vibrant fish, live rock, and reef ecosystems into your home. They reward patience and consistency, especially when it comes to salinity, water stability, and stocking pace.

Getting started with marine tanks

Marine setups are less forgiving of rapid changes than most freshwater tanks. The goal is simple: stable salinity, stable temperature, and a fully cycled biofilter before you add sensitive livestock.

1. Choose your direction: fish-only (FO), fish-only with live rock (FOWLR), or reef.
2. Mix saltwater correctly and confirm salinity with a reliable refractometer.
3. Cycle the tank fully (live rock helps) before adding fish or inverts.
4. Stock slowly. Marine biofilters adapt best with time.
5. Keep stability: top off evaporation, test regularly, and avoid big parameter swings.

Salinity Cycling Reef basics Common mistakes

What you'll typically need

A stable mixing and top-off routine matters as much as the hardware.

Tank + heater + filter (or sump)
Salt mix + mixing container + circulation pump
Refractometer and a basic test kit
Top-off plan (manual or ATO) for evaporation

What is marine fishkeeping?

Marine (saltwater) fishkeeping focuses on maintaining a stable saltwater environment for fish, invertebrates, and optional corals. Compared to freshwater, the core challenge is controlling salinity and avoiding rapid swings in water chemistry.

Many marine tanks use live rock and biological filtration to support a diverse microbial community. As your tank matures, it becomes more resilient, but early stability and slow stocking are critical.

What you'll focus on

Stability first: salinity, temperature, and consistent top-off
Filtration and oxygenation: flow, surface agitation, and export
Smart stocking: compatibility, territory, and gradual additions
Long-term consistency: maintenance routines over "quick fixes"

The 4 fundamentals (and why they matter)

Marine success is mostly about stability. Salinity swings from evaporation, rushing the cycle, or adding too much too fast are the most common causes of early losses.

Cycle first: Establish biological filtration before adding livestock. Live rock helps, but time is still the key ingredient.
Stable salinity: Evaporation raises salinity quickly. Top off with fresh water (not saltwater) to keep salinity stable day to day.
Right equipment: Strong flow, reliable heating, and good filtration matter. Reef tanks often add lighting and nutrient export equipment.
Stock slowly: Many marine fish are territorial. Add the most peaceful fish first and give your system time to adapt.

Thinking about a reef tank?

Reef tanks can be incredibly rewarding, but they raise the bar for stability and equipment. Start simple and let your tank mature before chasing fast growth or sensitive corals.

Choose hardy starter corals and build slowly
Keep light and flow consistent
Focus on stable parameters over chasing numbers

Common mistakes (easy to avoid)

Letting salinity swing because of evaporation
Adding fish before the tank is fully cycled
Overstocking early (biofilter and territory issues)
Mixing aggressive or incompatible species
Making big parameter changes to "fix" minor problems

New to marine fishkeeping?

Marine tanks are absolutely beginner-friendly if you approach them with a stability-first mindset. Go slow, keep salinity consistent, and let the tank mature.

Go slow: add livestock gradually.
Top off: evaporation changes salinity fast.
Keep it stable: consistency beats "perfect" readings.