The best places to buy saltwater aquarium supplies online are Amazon for everyday gear and consumables, Chewy for food and medications, and specialty retailers like Marine Depot, BRS (Bulk Reef Supply), and Aquacave for reef-specific equipment. Local fish stores simply can't match the selection or prices available online, especially for niche saltwater gear like protein skimmers, calcium reactors, and reef lighting.
This guide covers which products to buy from which online stores, how to find genuine products from established brands, and how to handle the logistical challenges of ordering saltwater-specific supplies. I'll also explain where to find the best deals and how to buy live products (coral frags, macroalgae, copepods) online safely.
The Best Online Retailers for Saltwater Supplies
Amazon
Amazon is the default starting point for most saltwater aquarium supplies. Prime shipping gets you test kits, filter media, salt mix, powerheads, and heaters in two days. The review volume on popular products is high enough that you can spot reliability problems before buying.
What Amazon does well for saltwater: - Bulk salt mix (Instant Ocean, Red Sea, Tropic Marin) - Test kits and reagents (Salifert, API, Red Sea Pro) - Powerheads and wavemakers (Jebao, Maxspect, Hydor) - Protein skimmers (Reef Octopus, Bubble Magus, Simplicity) - Heaters (Eheim Jager, Fluval, Aqueon) - Lighting (Kessil, AI Hydra, Maxspect, Ecotech Radion) - RODI systems and replacement membranes - Aquarium salt mixes
What to watch out for: Third-party sellers on Amazon sometimes sell counterfeits of popular brands, particularly for LED lights and controllers. When buying Ecotech Marine, Kessil, or AI products, buy directly from the brand's authorized Amazon storefront or a major retailer. Check the "Fulfilled by Amazon" designation as a starting point for legitimacy.
Bulk Reef Supply (BRS)
BRS is the top choice for reef-specific supplies and the best educational resource in the hobby simultaneously. Their YouTube channel has thousands of hours of tutorials that pair directly with the products they sell. If you're buying a dosing pump, calcium reactor, or two-part solution, BRS will have a video explaining exactly how to use it.
BRS sells their own house-brand products (BRS 2-Part, BRS carbon, BRS GFO) at competitive prices that are genuinely good quality. Their reactor media and carbon in particular are consistent and cost-effective. They also carry Triton, Brightwell Aquatics, and Two Little Fishies chemistry products.
BRS is also the best source for RODI replacement parts: membranes, DI resin, sediment filters, and carbon blocks for their own units and compatible third-party systems.
Marine Depot
Marine Depot competes with BRS for the specialty saltwater market. They tend to carry a slightly wider equipment range and sometimes have better pricing on specific premium brands like Tunze and Ecotech Marine. Their saltwater-specific category filters make it easy to find exactly what you need for a reef setup.
Marine Depot is worth checking for: - Tunze equipment (protein skimmers, powerheads, auto top-off units) - Ecotech Marine Radion lights and Vortech powerheads - Innovative Marine tank systems - Aqua Illumination Hydra lights - Red Sea MAX systems and accessories
Chewy
Chewy handles food and medication better than anyone else. Their auto-ship pricing on fish food is typically 30 to 35 percent below retail, and their return policy is exceptional. For frozen foods (mysis shrimp, brine shrimp, krill), check whether they ship frozen to your area. Chewy offers next-day delivery in many markets with insulated packaging.
Chewy carries: - Hikari frozen foods and pellets - New Life Spectrum pellets - Two Little Fishies coral foods - Brightwell Aquatics supplements - Fritz Turbo Start and API saltwater medications
Premium Aquatics and Aquacave
For livestock (coral frags, fish) and harder-to-find equipment, Premium Aquatics and Aquacave both carry curated stock and actually know what they're selling. Premium Aquatics in Indiana ships livestock nationwide and has a reputation for healthy stock. Aquacave focuses more on equipment and carries some brands that other retailers don't.
For a comprehensive breakdown of top-rated products across categories, the best aquarium supplies online guide has detailed comparisons.
Salt Mix: The Most Important Consumable Purchase
Your choice of salt mix determines your baseline chemistry and affects everything from coral growth to fish health. Don't cheap out here.
Instant Ocean: The long-standing standard. Consistent chemistry, widely available, competitively priced. A 200-gallon bucket runs about $65 to $75 on Amazon. Good for fish-only and reef tanks where you supplement calcium and alkalinity separately.
Instant Ocean Reef Crystals: Elevated calcium and alkalinity levels for reef tanks, same price range as Instant Ocean.
Red Sea Coral Pro Salt: Elevated calcium, alkalinity, and magnesium. Popular with SPS coral keepers who want a higher baseline before dosing. Around $80 to $90 for a 175-gallon bucket. Dissolves cleanly with minimal cloudiness.
Tropic Marin Pro Reef: Premium option from a German manufacturer, $90 to $100 for 200 gallons. Extremely consistent batch to batch, good for sensitive systems.
Fritz RPM Salt: Newer option that has gained traction among serious reefers. Similar chemistry to Red Sea Coral Pro at a slightly lower price point.
Buy salt in the largest size that fits your storage space. The per-gallon cost drops significantly in larger buckets. Store open containers in a cool, dry location with the lid sealed tightly between uses.
RODI Water: Essential for Saltwater Tanks
Using tap water directly in a saltwater tank introduces phosphates, nitrates, chloramine, silicates, and other compounds that cause algae blooms and stress corals. RODI (reverse osmosis, deionized) water removes these completely, starting with a TDS reading of 0.
You can buy RODI water from a local fish store (typically $0.25 to $0.50 per gallon) or invest in a home RODI unit. For tanks over 50 gallons, a home unit typically pays for itself within a year.
BRS's 4-stage RODI system runs around $170 and is the most popular home unit in the hobby. The 75 GPD (gallons per day) membrane handles tanks up to about 100 gallons comfortably. For larger systems, a 150 GPD membrane version is available.
TDS meters (around $15 on Amazon) verify your RODI is working correctly. If your output TDS is above 5, replace the DI resin. If it's above 0 with fresh DI resin, your RO membrane or pre-filters need replacement.
Additives and Supplements: What to Buy and When
For a fish-only saltwater tank, water changes alone handle chemistry maintenance. You need salt mix, water conditioner (Seachem Prime works in saltwater), and basic test kits. Nothing else is required.
For reef tanks, you need to maintain calcium, alkalinity, and magnesium as corals consume them. The main approaches:
Two-part dosing: Equal parts calcium chloride and sodium bicarbonate solutions dosed daily or via a dosing pump. BRS 2-Part is the standard product. Cost-effective for tanks consuming less than 150 ppm calcium per week.
Kalkwasser: Calcium hydroxide dissolved in RODI water, dripped in as part of auto top-off. Raises both calcium and alkalinity simultaneously while also precipitating phosphate. Nelson's Kalkwasser from BRS is commonly used.
Calcium reactor: Uses CO2 to dissolve calcium carbonate media, releasing calcium and alkalinity into the water. Higher upfront cost but cheapest long-term for large systems with high demand.
For trace elements consumed by SPS corals (iron, potassium, strontium), Triton Method and Brightwell Aquatics supply complete dosing regimens. Start with the basics, test regularly, and add supplements only after identifying specific deficiencies.
Check the best aquarium supply online store for more vetted retailer options and pricing comparisons.
Buying Livestock Online
Yes, you can buy fish and coral online, and many hobbyists do so successfully. The main risks are DOA (dead on arrival) from shipping stress and disease introduction. Mitigating both requires some planning.
For fish: LiveAquaria and Diver's Den are the most established online fish retailers. LiveAquaria's Diver's Den section offers specific individual specimens photographed in their facility, which eliminates the guessing game of wild-caught quality. They guarantee live arrival. Check their online store notes for the collector origin and CITES documentation on sensitive species.
For coral: Reef2Reef's Marketplace connects hobbyist sellers who frag their own colonies. Local reef clubs and regional swaps are also excellent sources. For aquaculture coral specifically, ORA (Oceans, Reefs, and Aquariums) produces colonies in Florida that arrive healthier than wild-caught alternatives.
Shipping requirements: Livestock must ship overnight with heat or cold packs as needed. Summer shipping above 85°F requires cold packs and insulated boxes. Winter shipping below 50°F requires heat packs. Never order livestock to ship over a weekend since packages sit in courier facilities on Saturday and Sunday.
FAQ
Is buying saltwater aquarium supplies on Amazon safe?
Yes, for most equipment and consumables. Stick to well-reviewed listings from Amazon's own fulfillment or authorized brand storefronts. For expensive equipment like LED lights or controllers, verify the seller is an authorized dealer by checking the brand's website. Returns are straightforward if something arrives damaged.
Why is BRS considered the best reef supply store?
BRS combines competitive pricing, broad inventory, and an exceptional amount of free educational content. Their YouTube channel and dosing calculators are genuine resources that help you use the products correctly. Their house-brand reactor media and chemicals are high quality. The combination of support and selection makes them a trusted source in the hobby.
Can I mix different brand salt mixes?
You can, but it's not recommended. Different brands use different ratios of minerals and additives. Mixing can cause precipitation events where calcium and alkalinity compounds crash out of solution. Stick to one salt mix and change brands gradually if you want to switch, by mixing the new salt into batches incrementally over several water changes.
How much should I spend on supplies for a new saltwater tank?
A basic 40-gallon fish-only saltwater tank setup including salt, test kits, a protein skimmer, powerhead, and heater runs $300 to $500 in supplies beyond the tank itself. A 40-gallon reef tank with lighting, a skimmer, and a two-part dosing setup is $500 to $900 in supplies. These are starting estimates; reef equipment scales up significantly with tank size and coral intensity.
Shopping Smart for Saltwater
Build your default shopping list: Amazon for equipment and salt, BRS for reef-specific additives and media, Chewy for food on auto-ship. Check Marine Depot when you need premium brand gear. Use a price tracker like CamelCamelCamel for Amazon items and watch BRS's weekly specials. The savings from buying consumables in bulk online versus a local fish store add up to hundreds of dollars a year on a typical reef system.