Setting up a marine aquarium takes more equipment than a freshwater tank, but you don't need to buy everything at once. The core supplies you need are a tank, a protein skimmer, a quality return pump, live rock, salt mix, a refractometer, lighting (especially for corals), and a heater. Get those right first, and you can add specialized gear as your tank matures.

This guide covers the full list of marine aquarium supplies, organized by what matters most, so you know what to prioritize and where you can cut corners without hurting your animals.

The Foundation: Tank, Sump, and Return System

Your tank is obviously the starting point, but the sump is what separates a manageable reef from a maintenance nightmare. A sump is simply a second tank, usually kept in the stand below the display tank, that houses your equipment out of sight. Running a sump gives you more total water volume, which buffers against swings in temperature and chemistry. For most hobbyists, a sump sized at 20 to 30 percent of the display tank is a good target.

Overflow Boxes and Drain Lines

To get water into the sump, you need either a tank drilled with an overflow (internal or external standpipe) or a hang-on overflow box. Drilled tanks with Herbie or Bean Animal overflow setups are quieter and more reliable than hang-on boxes, which can lose siphon during a power outage. If you're buying a new tank, get it pre-drilled.

Return Pumps

The return pump sends water back up from the sump to the display. Jebao DC series pumps (the DC-2800 handles tanks up to 50 gallons, the DC-6000 works for 100+ gallon systems) are popular because they're variable speed and energy-efficient. Reef Octopus and Ecotech VarioS pumps cost more but run quieter and have better build quality for larger systems.

Size your return pump at 3 to 5 times the display tank volume per hour, accounting for head pressure from the vertical lift back to the tank.

Filtration: Protein Skimmers and Mechanical Media

A protein skimmer is the most important piece of filtration equipment in a marine tank. It pulls dissolved organic compounds out of the water before they break down into nitrate, which is far easier to manage than trying to export nitrate after the fact. For a well-stocked reef, a properly sized protein skimmer can cut your water change frequency in half.

Sizing Your Skimmer

Manufacturer ratings are almost always optimistic. A skimmer rated for 150 gallons will realistically handle a lightly loaded 100-gallon system. For a heavily stocked fish-only system or a nutrient-heavy reef, drop the rated capacity by another 25 percent. The Reef Octopus Classic 110-INT (rated 110 gallons) works well for 75-gallon display tanks. The Bubble Magus Curve A9 (rated 250 gallons) is a step up for 120 to 180-gallon builds.

Mechanical Filtration

Filter socks (usually 200 to 400 micron) catch large particulates before they decompose. The downside is they need rinsing every 2 to 3 days or they become a nitrate factory themselves. Filter rollers from companies like Clarisea and Aquamaxx automate this process with fresh filter fleece that rolls forward when the sock gets dirty. They cost $200 to $400 upfront but save significant maintenance time.

Lighting for Corals and Fish

Lighting requirements split into two categories based on what you're keeping. Fish-only tanks can run any light that makes your fish look good. Reef tanks with corals, especially light-hungry SPS (small polyp stony) corals, need much higher intensity and the right spectrum.

LED Fixtures

LED technology has made reef lighting more accessible. The AI Hydra 32 HD covers a 24-inch square footprint and is suitable for mixed reef tanks with LPS and some SPS corals. The Radion XR15 Pro and XR30 Pro from Ecotech are considered the gold standard for SPS-heavy systems, with precise spectrum control and EcoSmart scheduling. For budget builds, the Kessil A360X delivers solid PAR output and great shimmer effects.

For a 4-foot tank, two Hydra 32 units or three Kessil A160WE units will cover most reef livestock.

T5 Fluorescent

T5 fixtures remain popular because they deliver even light coverage without hotspots. Hybrid builds that combine T5 tubes with a central LED fixture give you the spectrum depth of T5 with the controllability of LEDs. ATI and Aquatic Life make hybrid fixtures purpose-built for this approach.

Circulation and Flow

Corals need flow for feeding and to prevent detritus from settling on them. Powerheads (also called wavemakers or circulation pumps) are positioned inside the tank to create random or pulsing flow patterns.

The Tunze Turbelle Nanostream 6095 and Ecotech MP10, MP40, and MP60 series are the dominant options. MP40 units run around $250 each and are appropriate for tanks from 50 to 200 gallons. Jebao and Hygger offer budget powerheads in the $30 to $80 range that work fine for fish-only setups or beginner reefs.

A general target is 10 to 20 times the tank volume in turnover per hour from your circulation pumps combined, on top of your return pump flow.

Water Chemistry: Salt, Testing, and Dosing

Marine tanks require stable salinity (1.025 to 1.026 specific gravity, or 35 ppt), temperature (76 to 80 F for most systems), alkalinity, calcium, and magnesium. These parameters fluctuate as corals grow, evaporation concentrates salts, and water changes shift chemistry.

Salt Mix

Instant Ocean and Fritz RPM are popular options that mix clean and reliably. Reef Crystals (by Instant Ocean) contains elevated calcium and magnesium for reef tanks. For SPS-heavy systems, Red Sea Coral Pro and Triton Method salts are formulated for tighter parameter stability.

Refractometers and Salinity

A refractometer calibrated with NIST-traceable calibration fluid is the right tool for measuring salinity. Swing-arm hydrometers are inaccurate and not worth using. The Milwaukee MA887 refractometer costs around $30 and is accurate enough for most hobbyists.

Testing

At minimum, test alkalinity, calcium, magnesium, ammonia, nitrite, nitrate, and phosphate. Salifert and Nyos test kits are accurate and reasonably priced. The Hanna Checkers (HI755 for alkalinity, HI713 for phosphate) give digital readouts that remove color-matching subjectivity.

Dosing pumps like the Neptune DOS or BRS Two-Part system automate alkalinity and calcium supplementation as corals consume these elements.

Live Rock and Sand

Live rock serves as your biological filter. Bacteria colonize its surface and process ammonia into nitrite, then nitrate. You need 1 to 1.5 pounds of live rock per gallon, though aquascaping trends have moved toward less rock for better flow and visual impact.

Dry rock (like Aquacultured Pukani or Marco Rocks) is pest-free but takes 6 to 8 weeks to fully cycle. Seeded live rock from a local fish store speeds the cycle but risks introducing pest anemones, bristle worms, or Aiptasia.

Aragonite sand at a 1 to 2 inch depth supports a natural sandbed biology. CaribSea Arag-Alive and Nature's Ocean Bio-Activ both contain beneficial bacteria that jumpstart the cycle.

If you're building your first marine tank and want to see what the full equipment list looks like as a curated set, our Best Aquarium Equipment roundup breaks down the top picks by category with pricing. For a broader comparison of filtration, lighting, and circulation options across different tank sizes, the Top Aquarium Equipment guide is a useful reference.

FAQ

Do I really need a protein skimmer in a marine tank?

For a fish-only tank with light stocking and regular water changes, you can manage without one. But for a reef tank or a moderately to heavily stocked FOWLR (fish-only with live rock), a skimmer makes nutrient management significantly easier. It's one of the most impactful pieces of equipment you can add.

How much does it cost to set up a marine aquarium?

A basic 30-gallon fish-only tank with a hang-on skimmer, basic lighting, and a powerhead runs around $400 to $600 in equipment. A 75-gallon mixed reef with quality lighting, a sump, and a proper skimmer typically runs $1,500 to $3,000 before livestock. You can spend far more on SPS-dominated systems with automated dosing and monitoring.

What's the most common mistake new marine tank keepers make?

Moving too fast. Adding fish or corals before the tank has fully cycled causes ammonia spikes that kill livestock. Wait until you have zero ammonia, zero nitrite, and detectable nitrate before adding anything living, and then add slowly.

Is RO/DI water necessary for a marine tank?

Yes, for practical purposes. Tap water contains chloramines, phosphates, silicates, and other compounds that cause algae problems and stress corals. An RO/DI unit (Reverse Osmosis / Deionization) removes these contaminants and produces water with a TDS (total dissolved solids) reading of 0. BRS (Bulk Reef Supply) makes reliable 4-stage and 5-stage RO/DI units starting around $100.

Wrapping Up

Start with the fundamentals: a quality skimmer sized slightly above your tank volume, a reliable return pump and sump, and lighting matched to your livestock. Get your water chemistry dialed in with a refractometer, accurate test kits, and a good salt mix before worrying about automation and dosing. The equipment can feel overwhelming at first, but almost every experienced reef keeper will tell you the same thing: the tank does most of the work once the biology is established. Your job is to not interrupt it.