Saltwater (SW) water changes get complicated fast because of the variety of systems out there: hang-on-back or canister filter setups, all-in-ones with a back chamber, and display/sump systems. Here's how to do it right regardless of which one you have.
What to Turn Off First
Scrape glass and surfaces before shutting anything off — leave filtration running to catch loosened debris
Hang-on-back or canister filters: unplug
All-in-one back chamber pump: unplug, so it never runs dry
Sump return pump: unplug, so it doesn't feed the display while levels are changing
Protein skimmer: unplug — fluctuating sump/chamber water levels can cause overflow and froth spillover
Wave makers and in-tank heaters: unplug if there's any chance they'll be exposed to air during draining
Tools You'll Need
A gravel vacuum/siphon — valve-style (like Aquatop), plain tube style (like Python), or self-starting bulb style all work equally well, it's a matter of preference
A fish net for catching floating debris
An acrylic-safe scrub brush/scraper if your tank is acrylic (a glass scraper will scratch acrylic)
Running the Siphon
Your collection bucket needs to sit below the tank for gravity siphon to work. With a plain tube siphon, submerge, fill with water, and lift just above the waterline repeatedly until flow starts. Valve-style vacs use a shake motion to prime the siphon faster. Pinch the hose to pause flow, let sand settle by gravity if you've pulled too deep, or free a fish that gets too close to the intake — they'll get used to the routine over repeated water changes.
How Much to Change
10–15% is the standard routine water change. If you need a larger correction (salinity, calcium, alkalinity), spread it across several days rather than doing 50% at once — a sudden large change is more likely to shock fish and corals than help them.
Refilling Consistently
Mark your normal water line (and sump line, if applicable) with tape once equipment is off and everything has settled. Refill to that same mark every time so your system runs consistently once everything powers back on.
Ready to build your water change routine? Shop gravel vacuums and aquarium maintenance tools at natureaquariums.com.
