How to do a water change in a shrimp tank

Published October 16, 2026 · Updated October 16, 2026 · 6 min read

A planted aquarium with tall green plants, small fish, round stones and driftwood on gravel — Photo: Aleš Tošovský, Wikimedia Commons, public domain (cropped)

Quick answer

Change a small amount: most guides suggest about 10 to 20 percent of the water, once a week to once every two weeks.
Prepare the new water first. Add water conditioner and match the temperature and hardness of the tank.
Remove old water with a siphon covered by a net or sponge, so baby shrimp stay in the tank.
Add the new water slowly.
Top up evaporation with RO or distilled water, not tap water.

Why water changes matter

Even in a clean, cycled tank, nitrate slowly builds up. Nitrate is the end product of the nitrogen cycle, where bacteria break down waste. It is much less harmful than ammonia or nitrite, but most guides suggest keeping it under 20 ppm (parts per million). A water change is the simplest way to bring it down.

For shrimp, how you change the water matters as much as how often. Shrimp react badly to sudden changes in temperature, hardness and TDS (total dissolved solids, everything dissolved in the water). A big, fast water change can upset their molt, when they shed their old shell to grow. A failed molt can kill a shrimp.

How much and how often

Shrimp guides give slightly different advice, but they all point the same way: small and regular.

Guide	Suggested water change
Shrimp Science	About 10% a week, or 20% every two weeks
The Shrimp Farm	Around 10% a week; avoid changes over 20%
Shrimp and Snail Breeder	About 20% a month for most keepers, which you can split into smaller changes
Flip Aquatics	15–20% every 7 to 10 days

So most guides land on changes of 10 to 20 percent, every one to two weeks. Several warn against changing more than 20 percent at once. A simple rule for beginners: test nitrate, and if it is above 20 ppm, do a water change.

In a 20-liter tank, 10 percent is 2 liters and 20 percent is 4 liters. That is about one large jug.

What you need

A bucket used only for the aquarium, never washed with soap.
Water conditioner that removes chlorine and chloramine, or RO water with shrimp minerals.
A thermometer, and if you have one, a TDS meter.
A small siphon or a length of airline tubing to remove water.
A fine net or a piece of sponge to cover the end of the siphon, so baby shrimp are not sucked out.
A white bucket, if you have one. It makes it easy to spot any baby shrimp you remove by accident.

Step by step

Test first. Check nitrate, and if you can, TDS and temperature. Write the numbers down, so you can compare them later.
Prepare the new water. Fill the bucket and add conditioner. If you use RO water, add shrimp minerals until you reach your usual GH (general hardness) or TDS, and let them dissolve completely before you use the water.
Match the temperature. Let the water reach room temperature, or check it against the tank with a thermometer. Many keepers prepare the water a day ahead.
Check the TDS. The new water should be as close to the tank water as you can get it.
Remove the old water. Cover the end of the siphon with a net or sponge and drain into the bucket. Light cleaning is enough. Some of the fine brown waste on the bottom, called mulm, is food for shrimp.
Check the bucket. Look for baby shrimp and put any you find back in the tank.
Add the new water slowly. Guides differ on speed. Some drip it in through airline tubing at 1 to 2 drops per second, like drip acclimation. Others pour slowly, a few liters per minute. The closer the new water matches the tank, the less the speed matters.
Check again. Look at the thermometer, and test again the next day.

Topping up evaporation

Water evaporates, but minerals don't. So as the water level drops, TDS and hardness slowly rise. If you top up with tap water or mineralized water, they keep creeping up, and that can lead to molting problems.

Top up with RO or distilled water instead, which has almost nothing dissolved in it. A lid on the tank also cuts evaporation. Remember that a top-up is not a water change. It only replaces the water that evaporated.

Common mistakes

Changing too much at once. More than 20 percent in one go is a common cause of failed molts.
Forgetting the conditioner, or using a bucket that had soap in it.
New water that is much colder or warmer than the tank. A sudden temperature change can trigger a molt, and berried females (females carrying eggs) may drop their eggs.
Topping up with tap water. TDS and hardness creep up over time.
Long gaps, then one big change. Keep the schedule regular instead.

If shrimp start dying after a water change, read our guide to why shrimp die. It explains what to check first.

FAQ

How often should I change the water in a shrimp tank?

Most guides suggest small changes of about 10 to 20 percent, once a week to once every two weeks. Testing nitrate helps: if it is above 20 ppm, it is time for a water change. Keep a regular schedule instead of long gaps followed by one big change.

Can I do a 50 percent water change in a shrimp tank?

It is risky. A big change shifts temperature, hardness and TDS all at once, which can trigger failed molts. Most guides warn against changing more than 20 percent at a time. The main exception is an emergency, such as copper or another poison in the water.

Do I need to vacuum the gravel in a shrimp tank?

Not deeply. Some of the fine waste on the bottom, called mulm, is food for shrimp. Clean lightly if waste piles up or you see a lot of detritus worms, and cover the siphon so baby shrimp are not sucked out.

Should I top up evaporated water with tap water?

No. Evaporation removes water but leaves the minerals behind, so topping up with tap water slowly raises TDS and hardness. Use RO or distilled water for top-ups, and save tap water for real water changes.

Sources

Shrimp Science: Shrimp Tank Water Changes
Shrimp Science: Why Are My Freshwater Shrimp Dying?
Shrimp Science: Total Dissolved Solids (TDS) for Shrimp Tanks
The Shrimp Farm: How To Properly Change Water on Your Shrimp Tank
The Shrimp Farm: Failed Molting in Shrimp
Shrimp and Snail Breeder: How to Do and How Often to Do Water Change in Shrimp Aquarium
Shrimp and Snail Breeder: How Long Do Dwarf Shrimp Live
Shrimp and Snail Breeder: Detritus Worms in Aquarium: Harmless or Dangerous?
Aquarium Co-Op: Care Guide for Cherry Shrimp
Flip Aquatics: Cherry Shrimp Guide
City of Sioux Falls: Chloramines and Fish (PDF)

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