Why are my Goldfish dying after a water change?


Your goldfish may be dying after a water change due to the rapid chemical composition changes that occur when a change in their water happens rapidly.

When fish live in a tank there are natural by-products such as discarded food, fish-waste, plant-waste etc. All of these (and other things) will, over time rot and degrade. This changes the chemical composition of the water within the tank. This change happens very slowly though over time and your fish get acclimatized to it. Then, when the water is changed, the chemical composition changes rapidly and this in-turn causes the fish to die.

This is a lot more common than you probably think. It’s surprising how many owners of goldfish have this problem and they don’t make the small changes necessary do it happens next time. There are some very simple steps you can take to get to the bottom of the problem and then fix it to ensure it doesn’t happen again!

If the fish don’t die they can become extremely stressed and then die weeks later. Discover what you should do.

The Dilemma – Should You Change Your Goldfish Water?

So, what should you do? Is there a point that you get to where you shouldn’t move your fish at all and it’s actually the safer option to just leave them be? Well, some people think that. But you do still have the option of changing the water, you’ve just got to do it the right way!

Options when Changing the Water

Your options depend on how long you’ve had your fish in the tank for. If it’s been a long time then you shouldn’t change all your water in one go. However, if it’s just been a few months then (as long as you get the job done properly) you should be fine.

Option 1 (Fish have been in the tank for over 6 months)

This, I think, is the easy option. It does take longer though. You must not change all the water in one go. What you need to do is change the water bit by bit, over time.

  • Week 1 – only change around 5% of the total volume of water, then leave it a good week.
  • Week 2 or 3 – change another 5% and leave it a week, remember there’s no real rush here and it’s really important that you don’t unsettle the fine chemical balance of the existing water too much. Monitor your fish between changes and if you see any signs of anxiety, stop.
  • Week 4 – after this second change, increase the amount of water that you change, first 10% and then up it to 15%. All the time, monitoring the behavior of your fish.
  • Week 5 – change 25% of your water. A good idea is to take a photo of the water before and after every change, you won’t notice much of a change initially but by now it’ll almost be as good as new.
  • Continue this a couple of times more and you’re done.

I know it takes quite a long time but it’s not difficult and if you want to maintain the health of your fish (and actually extend their lifespan) then this is the way to do it!

Option 2 (Fish haven’t been in the tank long)

This is a bit more complicated than option 1 but it’s still not too tricky. Follow these steps and you’ll be fine!

Relocate Your Fish

You will need two containers. One should be a suitable size to place your fish in while you clean and refill their permanent home. The other container should be able to hold at least the same amount of water as your current fish tank. Ensure that neither container has been washed with soap or other cleaning agents as the residue from these can be harmful to fish.

Age the water

Fill both containers with clean water from your tap and age them overnight in the same area as your fish tank to allow them to reach the same water temperature and to allow the levels of chlorine in the water to neutralize. If you don’t have time to age overnight, then you should treat thewith a suitable dechlorinator. This will neutralize the chlorine levels found in most tap water. It is important to make sure the water in both is the same temperature as the water in your permanent bowl or tank. You may like to have a lid handy to cover the container you plan to put the fish in to stop them from jumping out.

Avoid Direct Light

Don’t place the temporary containers near a window or under a bright light, as the heat from these could raise the water temperature and potentially harm your fish. Also, make sure you place your temporary tank in a place where children and other household pets can’t bother the fish.

Move Your Fish

When the water in your temporary tank is ready, use a fishnet to carefully scoop your fish out of their tank and place them gently into the temporary holding tank. Ensure the temporary tank is large enough so your fish have plenty of room to swim. 

When using a fishnet to transfer fish from one container to another, make sure your tank and temporary tank are close together so as to reduce the amount of time the fish is out of the water, thus reducing its stress levels. If you don’t have a net, you can use a small, clean bowl to transfer your fish. Make sure the bowl does not have soap or soap residue on it and select a rounded bowl with smooth edges. When using this method, simply submerge the small bowl into the fish tank and allow the fish to swim into it. You must be patient and avoid chasing the fish around its bowl as this will stress your fish.

Monitor your fish carefully

While you are cleaning their tank or bowl, make sure to keep a close eye on your fish in their temporary tank. Look for changes in their behavior, color and activity levels.

The following signs should be an indicator that the water in the temporary tank is too warm:

  • hyperactivity
  • changes in the fish’s color and
  • “yawning” at the surface of the water.
If the water is too cold, your fish may exhibit the following signs:
  • inactivity
  • sitting on the bottom and
  • changes in color.

Refresh the contents of your fish tank or bowl

Remove dirty water

Tip out the old water from your fish tank or bowl. Use a net, sieve or filter to keep the solid contents from falling out of the bowl and down your drain.

Clean the solid contents

Scrub the gravel and other decorations in your bowl with warm water and a little bit of salt. For the best results, place the gravel and decorations in a mesh sieve and scour with hot water from your sink. Once they are thoroughly rinsed, set them aside and allow them to cool.

Clean the bowl

Scrub the fishbowl/tank with warm water and salt. Again, avoid soaps and cleansers at all costs as they may leave a harmful chemical residue behind. Then, rinse the bowl thoroughly with warm water. If there is a noticeable buildup of limescale, clean it with vinegar then rinse thoroughly with warm water.

Allow the bowl to sit

After cleaning and rinsing the fishbowl, allow it to sit for 20 to 30 minutes. This will give the glass of the bowl time to cool down from its exposure to the warm water used to wash and rinse it out. Allowing the bowl time to return to room temperature will help to ensure the bowl is the ideal temperature when the fish are returned.

Refilling your fish bowl or tank

So now you need to refill your bowl or tank by following these steps:

  1. Replace the gravel and decorations. Place the gravel and any decorations back into your clean fishbowl ready to add clean water. Make sure everything is arranged the way it was as fish can be sensitive to changes to their environment.
  2. Refill the bowl with clean, aged water. Fill your fish bowl or tank o the correct level with aged or dechlorinated water from your second container.
  3. Place the fish back in their freshly cleaned tank or bowlPlace your fish back into the fishbowl that has been filled with clean water. Take your time and gently lower the fish into the water using a net or a bowl. Do not shock your fish by dropping them in. Keep the water in the temporary tank in case your fish don’t settle in their cleaned water.

Monitor your Fish after Changing the Water

Fish are most likely to experience stress and environmental or temperature related illnesses during and immediately after cleaning their tank. So, keep a close eye on your fish after putting them back in their bowl to ensure they are adjusting well to their cleaned environment. If they show any signs of distress you can move them carefully back to the temporary tank whilst you address any issues with their newly cleaned home.

So, I really hope that’s helped. Good luck, these tips have been proven to work before so I do hope they will work with you!

Jane

I'm Jane Pettitt, co-owner of Pets Knowledge Base with my husband, Matt. I have a grand total of 50 years’ experience as a pet owner. It all started with a guinea pig called Percy when I was 5 years old and since then I’ve lived with two more guinea pigs, a hamster, mice, a rabbit, a tortoise, a dog and 11 cats. I’ve learned so much about pet care during this time and many of my articles are based on my personal experiences and those of my family and friends .

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