How to Do a Water Change the Right Way — Gravel Vac Tips & Common Myths Busted

Water changes are the single most important maintenance task in fishkeeping — and one of the most misunderstood. In this video, Henry from Nature Aquariums clears up the most common misconceptions, walks through everything you need, and shows you exactly how to do a water change and gravel vac the right way without stressing your fish or making a mess.

Common Myths — Let's Clear These Up

Myth: You need to remove your fish to do a water change. No. Leave them in the tank. Fish are fine with you working around them and will get used to the routine quickly.
Myth: You need to scrub down and disinfect the whole tank. Never use household chemicals in an aquarium — ever. Even products that seem harmless can contain surfactants or cleaning agents that will harm or kill your fish. Clean with aquarium-safe tools only.
Myth: Water changes are complicated and time-consuming. With the right setup, a routine water change takes minutes.

What You Need

Net — for removing floating debris before you start
Scraper or scrubby pad — for cleaning algae off the glass. Always buy aquarium-rated scrub pads — supermarket versions may have chemical treatments built in that are not fish safe.
Toothbrush — for getting into silicone corners without scratching
Gravel vac (siphon) — the core tool. Three styles available:
- Standard (Python-style) — simple tube and hose; you start the siphon manually
- Self-starting (Aquatop-style) — has a small internal valve; start by pumping up and down in the water
- Squeeze bulb (Fluval-style) — squeeze the bulb to initiate suction; easiest for beginners
Bucket — must sit lower than the tank; siphons will not work if the bucket is higher than the water level

The Right Order — Clean First, Then Siphon

Always clean the glass before you start removing water. Scrape algae off the glass, get into the silicone with a toothbrush, and stir up any debris — all while your filters are still running. The filters will pick up the floating particles. Once you're ready to siphon, then turn off your filters and heater before you start pulling water out.

Why turn off the heater? If you remove enough water that the heater becomes exposed to air while it's still on, it can shatter. Don't risk it.

Filters by type:

Hang-on-back and canister filters — unplug before siphoning; they can't run dry
Sponge filters — air-driven, so they can stay on; nothing to damage

Starting the Siphon

Standard gravel vac: submerge the tube in the tank, fill it with water, then quickly drop the hose end into the bucket below the tank. Gravity does the rest. To pause, pinch the hose. When you move buckets or reposition, always drain the hose downward after lifting it out so you don't drip on the floor.

Self-starting vac: submerge and pump up and down until flow starts. Many include a hose clip to pause without pinching.

Gravel Vac Technique

Gravel/non-planted tanks: push the tube down into the gravel and let it swirl. Debris, uneaten food, fish waste, and detritus will get sucked up while the heavier gravel falls back down. If you're pulling up too much gravel or sand, pinch the hose to pause — everything drops back down.

Planted tanks with aqua soil: do not jam the tube into the substrate — you'll destroy your scape. Instead, wave your hand just above the substrate surface to lift detritus up into the water column, then vacuum it while it's suspended. Work gently and methodically.

Fish getting too close? Keep a hand near the tube opening. If a small fish gets near, pinch the hose — they'll swim right out. Fish learn quickly and most will move out of the way on their own after a few sessions.

How Often and How Much

Henry's recommendation: 10% weekly water changes as standard maintenance. Avoid large single water changes — they stress fish and disrupt water chemistry more than smaller, more frequent changes.

Never change more than 20% at one time under normal circumstances.

Exception — heavily medicated or heavily polluted tank: instead of doing one large change, do 10% daily for 5 consecutive days. You'll achieve the same total volume replaced (50%) without the shock of a single large change.

Bonus Tip — Cleaning a Sponge Filter

Grab a large Ziploc bag, submerge it in the tank, lift the sponge filter into the bag underwater, then squeeze the sponge into the bag to release the trapped waste. Pull the bag out with the dirty water inside and discard. The beneficial bacteria stay in the tank, the gunk goes in the trash.

Video Chapters

0:00 — Introduction: the easiest way to do a water change
1:00 — Common myths debunked: fish removal, chemicals, difficulty
2:30 — Tools you need: net, scraper, scrub pad, gravel vac, bucket
4:00 — Three types of gravel vacs and how each works
5:30 — Order of operations: clean glass first, then siphon
6:30 — Filter and heater shutdown: what to turn off and why
7:30 — Starting a standard siphon gravel vac
9:00 — Starting a self-starting gravel vac
10:00 — Gravel vac technique for non-planted tanks
12:00 — Gravel vac technique for planted tanks with aqua soil
13:30 — What to do if fish get too close to the siphon
14:30 — How often and how much: weekly 10% recommendation
15:30 — Bonus tip: cleaning a sponge filter

Bottom Line

A 10% weekly water change with a good gravel vac is one of the simplest things you can do to keep your fish healthy and your tank looking great. Clean the glass first, turn off your equipment, siphon out the waste, and refill with treated water. That's it. Do it consistently and your fish will thrive.

We carry gravel vacs, scrapers, aquarium-safe scrub pads, and everything else you need for easy tank maintenance at natureaquariums.com — shipped right to your door.