Why do My Guppies Keep Dying? What Should I Do?

An opulent aquarium filled with colorful guppies can make an impact on anyone and fill your home with color and energy. Although guppies are tropical fish, they are easily domesticated, capable of adapting to pretty much any aquatic environment. However, as a guppy lover, you need to know what you’re doing if you plan on raising guppies.

That’s because any mistake, no matter how small it can appear to you, can affect your guppies severely. And there’s nothing scarier than having your guppies die for no apparent reason. If you notice your guppies acting weird, lethargic, refusing food, or straight up giving up on life, it’s time to act.

Here are several potential causes for why your guppies keep dying:

Polluted, Poisoned, or Unclean Water

Water quality is key for your guppies’ health and life quality. And there are a lot of things that can go wrong in this department. Some of the most common water problems you should pay attention to include:

  • Toilet habits pollute the water – Like any other creature, guppies take in food through one end and eliminate the leftovers through the other. Their waste will accumulate on the aquarium bed and, shortly, will begin polluting your guppies’ environment, causing them to go sick or straight up die. Cleaning your water regularly should help you avoid this issue.
  • Unfit water – I include here poorly oxygenated, too cold, and too hot water. Either of these will cause life-threatening problems for your guppies for obvious reasons.
  • Using tap water – Tap water contains chlorine, which is unfit for your guppies. You should always treat the water first before adding your fish in and risking a catastrophe along the way.

Skipping the Cycling Process

If you’re new to this, aquarium cycling is the first notion you should become accustomed to. The process refers to several steps required to cleanse the tank and make it feasible for the fish. The underlying goal is to eliminate any ammonia, nitrates, and nitrites that can affect your guppies with potentially deadly consequences.

There are three core steps to follow here:

  • Fill up your tank with water
  • Add a de-chlorinator
  • Add nitrifying bacteria

The cycling process will begin and will usually last around 1 to 2 weeks. If you think that’s too long, too bad – you need to do it to protect your fish. After the 2-week period, I recommend using an API Test Kit to check for ammonia and nitrate levels and make sure everything is within charts.

Ammonia Build-up

This is probably one of the most common causes of dead aquarium guppies around the world. The reason is that many things can cause a spike in ammonia levels, and it’s easy to overlook them. Miss one, and the consequences can be devastating. Several things can cause an ammonia spike in the water, including:

  • Unconsumed fish food – Many fish owners tend to throw in more food than their fish can eat. It’s all due to comfort, you see. Why should you struggle to remember to feed your fish every 3 hours when you could throw a day’s worth of food in and go on with your life? The problem is that all the leftovers will build on the tank’s substrate and begin to rot shortly, causing a consistent build-up of ammonia over time.
  • Dead fish – Fish can and will die despite all your best efforts. It can be due to sickness, cannibalism, or simply because their time is up. The problem is that if you don’t pay attention, they may sink and disappear in the substrate or the aquarium’s vegetation. Their rotting bodies will eliminate ammonia, gradually dragging the remaining living fish into the nether realm.
  • Unclean waters and dirty substrate – It’s pretty much the same thing because a dirty substrate will muddy the waters and vice-versa. Keeping the water clean will protect your guppies against health issues and death.

Before closing this paragraph out, here’s a fun and interesting fact about ammonia. Even if you eliminate it before your fish start dying, they might start dying anyway. The process responsible for that is called ammonia burn. It might be fatal for them if they get it, despite the API Test Kit showing a 0 value on the counter.

It makes you take the problem more seriously, doesn’t it?

Too Much Food

Overfeeding is a major problem for most guppy owners due to its perceived comfort. You just throw some fish food in the tank and call it a day. Your guppies will eat as much they can then leave the rest, and everything will be good, right? Wrong. There are two problems here worth mentioning:

  • Guppies are greedy – No, greed is not exclusive to human beings. If you’ve ever had dogs or cats, you’ve probably noticed they tend to gorge themselves if you provide too much food. The same goes for guppies with similar health issues along the way. Have you ever seen an obese guppy trying to stay afloat? Feed yours too much, and you will.
  • Rotting food – The unconsumed food will spoil in the tank’s substrate, leading to, you guessed it, ammonia build-up. And we all know that this substance can do by now.

I recommend feeding your guppies several times per day, every 3-4 hours or so, and only what they can eat in 20-30 seconds at once. This will prevent overfeeding and protect your guppy population from dire consequences over time.


I know that having a tank full of colorful fish is every guppy passionate’s dream. Nothing beats the sight of having several dozen guppies flock inside a vegetation-rich aquarium, causing myriads of rainbow-style light sparkles. Unfortunately, that sight comes with its specific risks. Overcrowding is a massive issue that may guppy owners tend to be oblivious to.

And if you think you can prevent the situation with ease, think again. A female guppy can produce between 20 and 120 offspring per month. Add in multiple females into the mix, and the situation can explode fast.

You need to monitor your guppy population carefully to prevent overcrowding, which could mean getting a new, bigger aquarium. Or two. Or becoming a professional guppy breeder. Who knows where that will take you.

Unfit Water Temperature

Guppies are very sensitive to water temperature changes. They can easily withstand some fluctuation, but more significant shifts will cause serious health issues. The ideal temperature for guppies lies in the 72-82 degrees F area. They can go as low as 64 degrees without dying immediately, but they will risk developing serious health problems along the way.

Warmer waters exceeding 82 degrees F can also have devastating consequences over time. Warmer waters burn out the oxygen, leaving less for the guppies. The result is a slow, dreadful, suffocating death.

Just make sure to use a water thermometer to keep the temperature in check, and everything should be fine.

Parasites and Illnesses

Several diseases could affect your guppies over their lifespan. These include:

  • Fin rot (some of the core symptoms are self-explanatory, including rashes and fin decay)
  • Flukes
  • Ick (the most common symptom involves white spots on the body)
  • Velvet (the appearance of gold dust all over the skin)
  • Guppy tuberculosis (a fatal disease linked to the mycobacterium which has no known cure)

Out of all these conditions, only the latter has no treatment. If you suspect some of your guppies have contracted tuberculosis, I advise removing them from the tank and put them out of their misery. Otherwise, they might spread the condition to others, and, last thing you know, you’ll be dealing with a guppy pandemic.

Poor Genetics

Unfortunately, if your guppies have poor genetic baggage, there’s little you can do. This is where getting your guppies from trusted sources is paramount. Pet stores are the lowest on that spectrum since pet stores don’t care about selecting guppies from the best gene pool. They’ll just get whatever they can get their hands on.

Don’t be surprised if your guppies will start dying for no apparent reason within the first months following the purchase. I recommend seeking experienced guppy breeders instead, which offer quality and guarantee for your guppies’ health and genetic pool.

How to Breed Healthy Guppies?

Despite what you may have read so far, guppies are not pretentious animals. Just give them some good water, regular and diverse food, and take care of their fry, and the guppy population will thrive. Here are a handful of things relating to a healthy guppy population:

Optimal Feeding

Guppies are omnivores, meaning that they will consume both meat and plant-based foods. “Variety” is the word of the day today. Keep their food as varied as possible to make sure they get all the nutrients they need daily.

Whether you buy their food or prepare some of it at home, there are a variety of options to choose from. We include here brine shrimp (live or frozen), bloodworms, algae, veggie pellets, flakes, spirulina tablets, etc. The same food choices apply to guppy fry as well.

Keeping the Water Clean and Fresh

Regular water changes are key when looking to keep your guppy population healthy and thriving. You should consider changing around 20 to 30% of the water at least once a week to ensure good results.

This will eliminate some of the toxins that accumulate with time and keep the water fresh and oxygenated. Don’t get lazy with it over time. I recommend keeping a tight schedule to make sure you don’t skip sessions.

Optimal Tank Maintenance

Maintaining your tank comes with several obligations, including:

  • Clean the internal and external filters once or twice per month – Don’t clean them in tap water, as this will eliminate the beneficial bacteria growing there. Clean them in the tank’s own water to preserve the bacterial cultures.
  • Vacuum the substrate – This will remove mock, food leftovers, and fish droppings that can accumulate with time and increase ammonia levels.
  • Clean the tank’s glass – Not a life-or-death requirement, but it pays off to have your aquarium looking clean and crisp.

Early Treatment Saves the Day

Diseases are your guppies’ worst enemy. The key is to pay attention to your guppies’ look and behavior and act as soon as you see something out of the ordinary. This includes suspicious behavioral patterns, spots or irregularities on the fishes’ bodies, lack of appetite, etc.

If you see some guppies acting weird, I recommend removing them from the tank and placing them in a different recipient. A small quarantine period should help you pinpoint the problem while keeping the other guppies safe.

Wrap Up

With a lot of guppies comes a lot of responsibility, goes the saying. Or something along those lines. The conclusion is simple – pay attention to what and how your guppies eat, clean the tank, change the water, and your guppies should thrive.

If this is your first time attempting to get into the guppy hobby, I recommend researching the topic a bit before jumping in head-first. Write a comment below, and I would be happy to share the light of knowledge with you.

avatar Noah
I’m Noah, chief editor at VIVO Pets and the proud owner of a playful, energetic husky (Max). I’ve been a volunteer at Rex Animal Rescue for over 2 years. I love learning and writing about different animals that can be kept as pets. read more...

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