Skip to content
Fish Supplies

Tanks and setupsChecklist

Saltwater Aquariums: What Changes From a Freshwater Tank

What changes when you move from a freshwater tank to a saltwater aquarium: the shared gear, the extra steps, and the freshwater chapters that still apply.

By Fish Supplies editorial teamUpdated 2 min readHow we research

We earn from qualifying purchases through links on this page. How we make money.

A saltwater aquarium uses the same core gear as a freshwater tank: a tank with a lid, a filter, a heater, a light and a test kit. What changes is the water. You mix marine salt into it, measure the salinity, and keep more readings stable, so plan for more testing and a slower start than a freshwater tank.

This section collects what is different about saltwater tanks. Much of the freshwater groundwork still applies, so the chapters below link back to it where it does.

Gear you already know from freshwater

A saltwater tank still needs a tank that the stand and floor can carry, a filter, a heater and a light. The ratings work the same way: size the filter and heater to the tank’s volume. Aqueon’s heater rule of 5 watts per gallon up to 55 gallons is a starting point for any heated tank. The setup checklist and fish tank sizes compared cover these basics.

Aquarium heaters, adjustable and preset

Shop aquarium heaters, adjustable and preset

Opens eBay in a new tab. Check condition, seller feedback and returns.

What is new in a saltwater tank

Saltwater needs a marine salt mix, made for aquariums, added to the water before it goes in the tank. You also need a way to measure how salty the water is, and you top up evaporation with fresh water, since the salt stays behind when water evaporates.

Step Freshwater tank Saltwater tank
Water Tap water with conditioner Water mixed with marine salt
Extra measurement None Salinity
Topping up Conditioned water Fresh water, since salt stays in the tank

Cycle first, the same as freshwater

A saltwater tank needs a colony of bacteria to break down ammonia from fish waste, just as a freshwater tank does, and fish should not go in until the cycle is done. VCA says a new freshwater tank needs 4 to 6 weeks; budget at least that long for saltwater. How to cycle a fish tank explains the nitrogen cycle and how to read a test kit.

Freshwater chapters that still apply

A clean, well-lit community aquarium with sand, plants and small fishThe setup checklistThe core gear every tank needs before fish.
A newly planted cube aquarium under a clip-on light, with no fish yetCycle a new tankThe nitrogen cycle and how to test for it.
Zebra danios swimming beside a filter outflow pipe and a stream of bubbles in an aquariumAquarium filtersHow each filter type works, and how to size one.

For the hardware in more depth, see the equipment section.

Part of Tanks and setups

Read next

Affiliate disclosure

Fish Supplies is reader-supported. Some links on this page are affiliate links: when you buy through them, we may earn a commission at no extra cost to you. As an eBay Partner, we may be compensated if you make a purchase through our links. Commissions never decide what we recommend or how we rank it. Listings and prices come from our partners and change often, so check the price, condition and seller on the retailer's page before you buy. Read how we make money.