How to Save a Dying Fish: Comprehensive Instructions

Last Updated on July 4, 2021 by cmoarz

When your fish starts to show signs of distress, it’s important that you know how to quickly and effectively save a dying fish. This article will provide you with comprehensive instructions on how to do just that! If these steps are followed correctly, then your little friend may have a chance at survival.

How to Save a Sick Fish

You want to isolate the sick fish in a quarantine tank. This gets it out of the environment it got sick in and keeps it away from other fish. You may need to add antibiotics to the quarantine tank if there is a disease and continue to do daily water changes. Fish antibiotics can be purchased without a vet. Consider following these diagnostic tools to determine what to do with your sick aquarium.

Diagnosing what went wrong

Let’s fix your dying tank! Read on.

A lot of things can cause fish to become sick. You need to diagnose how your fish got ill in order to make sure you’re giving it the right treatment as well as prevent other fish from the same fate. Isolate one of these factors and try a new plan if first doesn’t work:

– water quality

– temperature

– light intensity

– feeding schedule

– The food it’s eating

I will break down all these for you.

Check your water quality

One of the most common causes of fish illness is poor water quality. First, make sure you’re doing your regular water changes as well as the tank cleaning in order to get rid of toxins that build up over time.

You may need to change how often or how much you clean depending on how many fish are present and how quickly they produce waste

If your tank is fully cycled, nitrite levels should be below 3.0 ppm and nitrates should never exceed 40ppm. If you are reaching these levels, you may need to add more bacteria as well larger water changes.

You should also be checking the chlorine levels in the water you are adding to the tank.

Any chlorine will kill all the beneficial cycle bacteria. If there is any chlorine at all 0>ppm mg/l you should immediately use a water conditioner to remove it.

Fix Your Water Quality

Using the right water is also very important. pH, hardness are important factors, and many fish species are different. Some are more sensitive to imbalances and require softer, or harder water respectively.

Goldfish, Arowana, beta, gourami, angelfish, guppy, cichlid, etc all require their own unique sets of water parameters, so be sure to research what your particular fish needs.

Lowering hardness and pH is easy, as is raising it. Many substrates such as volcanic stratum will lower these values. Cuddlebones and powdered calcium can raise it.

And of course, never change out your filter. If you need to change it for any reason, place a new filter behind the old one for several weeks before removing the old one. This keeps the beneficial bacteria intact and is called “seeding”.

If you just can’t seem to keep your nitrites and nitrate levels under control, consider rebalancing your tank. You might be overstocked (too many fish for the amount of water and filtration).

Why Are large water changes needed?

Sometimes a large water change is necessary in order to keep the water quality and chemistry under control. The better balanced your tank is, the smaller the water changes can be.

For unoptimized tanks, larger water changes will be needed to maintain balance and safe water parameters.

An understocked tank can be the difference between a 25% water change once a week to a 50% water change every 3-4 days. Understocking your aquarium is always going to be an ideal solution.

The bioload from an overstocked tank will just make it impossible to keep up without a ton of onhand maintenance.


Every fish species has its own ideal temperature range. This can vary between species and how you care for your fish, but in general, the range is from 73 to 79 degrees Fahrenheit. Be sure to research the fish species you have.

The fix for this is simple, get a thermometer for your aquarium and either add a heating element or a cooling element depending on your needs.

Remember, room temperature might be fine one day, but it can swing very quickly if you don’t have a way to regulate the temperature. 10-degree changes overnight aren’t uncommon and it’s very hard on your fish.

Also, consider regulating the temperature of the room the tank is in instead if you have a large aquarium room.

Temperature rising or lowering too fast

When doing water changes, it’s very easy to shift the temperature of the water and that will cause stress and illness in your fish, It could outright kill it within a matter of minutes.

The best way to avoid this is to have conditioned water for water changes already at the temperature your tank requires. Some people use large jugs to hold the water while it comes to room temperature, and others have heaters and coolers.

The easiest way to lower fluctuations is to allow the water to sit on the counter for a while so it comes up/down to room temperature before being added to the tank.

The smaller the tank, the easier it is for fluctuations to happen. An 80-gallon tank could theoretically run water changes directly from the tap (with conditioner placed in the tank), while smaller 10-gallon tanks would surely perish if done in that manner.

Test water that is being added (tap water etc)

Aside from temperature, you should also consider testing your tap water with a test kit. Check for metals, (copper, iron, zinc), chlorine, hardness, calcium, alkalinity, etc.

Putting bad water in your tank will nullify everything you are trying to do.

Feeding schedule

Be sure you aren’t overfeeding or underfeeding your fish. This can easily be determined by how much food your fish is eating. If there is uneaten food left after feeding then your probably giving them too much too often.

With a bit of experimentation, you can easily adjust your feeding schedule by measuring how much you give them, and removing what they don’t eat. Then give them less the next time until there are no more leftovers.

This process will need to be replicated every time you add a new fish.

Check Your Fishes’ Food

Some fish are very very sensitive to certain ingredients in commercial fish food. The biggest culprit is often copper sulfate or other copper derivatives, which are added to help the fish absorb more of the other vitamins and nutrients in their food as well as act as a cheap cost preservative.

If you suspect that this might be your problem, try switching to a brand without copper sulfate or any unknown ingredients.

Animals especially sensitive to copper sulfates are shrimp, snails, and other gastropods, bivalves, and crustaceans.

You can read more about copper and find a list of safe foods here.

The food you may be providing might not be the right food for your fish. Be sure to get brands that are labeled specifically for your species to make sure they get all the nutrients they need to survive and be healthy.

Light intensity

lights are an important factor in the health of your aquarium fish and plants. They all need light to a certain degree to flourish just like anything else.

The problem can crop up if the light is too dim, too powerful. Another issue, depending on the light, is heating.

New LED-style aquarium lights don’t produce much heat, but if you are using an older bulb style light, consider replacing it as it could be increasing the temperature of the tank by a huge amount.

If your bad at turning your lights off at night and on in the day, consider adding a timer.

Fish have a circadian rhythm just like humans do, so always try to keep it as close to the natural cycle of day and night.

If you want to take it one step further, The tank should also have different lighting during these times too; for example, daylight or moonlight. But that’s a bit sweaty and try hard for most people and it really doesn’t make too much of a difference. You can always get natural moonlight from a window as well.

My fish is dying, how do I save him?

No matter if your trying to save a dying goldfish, or a beta, angelfish, guppy, cichlid, or Arowana, or any other, Most of the steps will be the same.

The first step is to remove the fish from the aquarium and place it into a fresh clean quarantine tank. Quarantine tanks usually have a filter, no substrate or decorations. It’s just water (preferably cycled and dechlorinated). Although in a pinch regular conditioned water will work here.

You want to keep this fish isolated and monitor how it reacts over the next few days and weeks. You may need to consider adding antibiotics to the quarantine tank if you think the fish is sick due to illness and disease.

You can buy antibiotics and have them overnighted to your house from amazon in a pinch, Or you can run down to the local fish shop/pet store and pick some up. It’s generally very cheap.

Meanwhile, You should be running diagnostics on the original aquarium as listed above. Check the water levels and change the water and filter media if necessary.

You may need to go as far as disassembling the entire tank and sterilizing everything if you think a disease is a culprit.

How To Comfort A Dying Fish

Sometimes, no matter what you do, the fish may still die. Fish are living creatures, after all. They are sensitive things.

If your fish seems like it’s suffering, and you wish to euthanize it, don’t flush it down the toilet.

Simply place it in a bowl with a bit of water and add a Lethal dosage of clove oil. 400mg should do the trick, feel free to up it as much as you want to make sure the end result is desirable.

The fish will feel nothing, she will fall asleep/lose consciousness almost immediately and pass on. If you want to be sure the deed is done, once she is unconscious, you may place her in the freezer. Never place a live, conscious fish in the freezer, it’s an agonizing death.

If your fish is just old, but not really suffering. Be sure to give her plenty of food, and fish pats if she likes that sort of thing. Be with her and enjoy her company like you would with a dying friend. Love her like she loves you <3

I’m very sorry for your loss.


Owner of and also owner of actual Aquarium Gravel believe it or not! ;). Setting up beautiful aquarium sceneries and habitats since I was very young. Enjoy!