Why Do My Guppies Keep Dying? Is There Anything I Can Do?

Guppy fish are popular freshwater aquarium fish among fishkeepers. Their striking colors and active behavior in the tank make them fun to watch. Guppies aren’t hard to take care of. In fact, they are very resilient types of fish. So, why do your guppies keep dying?

6 Key Reasons Why Guppies Keep Dying

Guppies Keep Dying Most of the time, guppies suddenly die because most beginners don’t know how to take care of guppy fish. The main reasons why your guppies may die include:

Poor Water Quality

The top reason why most guppies die in an aquarium is the quality of the water. Poor water quality can lead to diseases and parasites that cause guppy to become sick and die. Things that lead to poor water quality include overfeeding and excess fish waste. if left unregulated, the build-up of toxins causes the fish to die. Too cold or too warm water can cause guppies to die. Guppies are tropical fish and need a certain temperature to thrive. You can buy an aquarium heater to keep the temperature stable. Tap water, unconditioned, contains chlorine which is deadly to fish.


If this is your first guppy tank, then you probably bought a few and put them in your brand new aquarium. However, a week later, all your guppies start to die. Why? Because you didn’t cycle the aquarium. The cycling process lasts for about 2 weeks depending on the size of the fish tank.

What Do You Need:

Step By Step Guide

  1. Setup the tank and put add tank water into it
  2. Add a de-chlorinator to the water
  3. Add nitrifying bacteria
  4. After about 1-2 weeks, beneficial bacteria colonize the entire tank.
  5. Test for ammonia, nitrite, and nitrate with an API Test Kit. Ammonia and nitrite should be at 0 ppm, while nitrate can be at a maximum of 20 ppm.
Once everything is favorable, you can add the guppy fish. A day after adding the fish, do another test to verify that the bacteria can keep up with the nitrogen cycle. Monitor the tank for at least one week.

Ammonia Level

Ammonia should always be kept at 0 ppm. That means that there shouldn’t be ammonia in the aquarium. With good bacteria, ammonia is turned into nitrites and then to nitrates. The nitrogen cycle discussed above. Here are some things that can cause ammonia levels to rise:
  • Leftover fish food.
  • Unremoved dead fish.
  • A dirty filter.
  • Dirty substrate.


Feed adult guppy fish once a day or once every other day. Overfeeding them can lead to health issues. Uneaten food pollutes the water.
See also  Why Do Guppies Eat Their Babies?


Too many fish in a single tank can mean lower oxygen levels. Lower oxygen levels are fatal to fish. Too many fish in a tank can be stressful for the entire fish community. Stress can cause fish to die. Always try to keep fish to a minimum.


Guppy fish favor water temperatures between 72-82°F (22-28°C ). Guppies can survive in water with temperature as low as 64°F (18°C), but the chances of diseases are very high. Temperatures above 82 °F (28 °C) can lower the oxygen level which can cause suffocation and eventually death.

How To Prevent Sudden Death in Guppies

Proper feeding, regular water changes, and tank maintenance help to protect your guppy fish and allow them to have a happy and healthy life.


A variety of quality food can increase your guppy fish’s lifespan. Tetra produces some of the best fish food in general. Flakes, vegetables (you can prepare at home), spirulina tablets, and blood worms are also good choices.

Water Changes

Changing the water of the tank weekly removes toxins and harmful bacteria. Changing 20-30% of the water once per week is ideal in most cases.

Tank Maintenance

You should clean the aquarium’s filter at least twice a month. You can rinse sponge filters using aquarium water. Do not use tap water as it kills off the good bacteria needed for your tank. Repeat the same with your other filters (internal/external). Rinse the biological filter with aquarium water. Never leave the sponge or filter out to dry. If it dries out, the beneficial bacteria will die. You can also vacuum the gravel (or another substrate) to remove food particles and waste trapped there. External sources:
Scroll to Top