Why Are My Glofish Dying? {How Do I Prevent It?}

Are you frustrated with your glofish dying? Are you thinking why are my glofish dying?

What happened and what can you do to stop this cycle of dead glofish?

Don’t be so hard on yourself because this article is meant for many fish keepers like you who have experienced the death in glofish. We’re here to help.

Why Are My Glofish Dying?

Improper cycling, poor water conditions, incompatible tankmates, overfeeding, illnesses that are all attributed to stress, eventually leading to their demise. 

Why Did My Glofish Immediately Die?

You bring your glofish home and you’re excited to introduce them to your tank. The following reasons may have caused your glofish to die so soon:

  • Poorly bred 
  • Rough travel
  • Previously infected
  • Not quarantined at first
  • Improperly cycled tank

Poorly Bred

Glofish are genetically engineered mostly from zebra danios that are designed to be fluorescent. They are not naturally occurring fish in the wild. The fact is, most glofish are inbred and some of them have not been cared for properly before your local fish store acquired them.

You may attribute a sudden death due to them being poorly raised before you had a chance to take care of them. This is most likely the case if they died on their first day.

Rough Travel

The act of snatching them out of their environment and placing them in a bag is enough to stress out the hardiest of fish. Glofish are not an exception. The transport of glofish to your home is a delicate process.

Proceed with care and keep in mind that most fish can handle 7-9 hours in a bag if it’s oxygenated. Otherwise, the clock is ticking, but rushing and swooshing around in the bag is detrimental to the health of your glofish.

Previously Infected And Not Quarantined

If your glofish arrived ill, it’s hard to tell right away. This is why many experienced fish keepers advocate that new arrivals should be quarantined in a separate tank up to 2 weeks before allowing them to enter your main tank’s ecosystem.

You can add tank water with daily water changes to keep the water pristine while making sure they get adjusted to the beneficial bacteria that is different from their tank of origin at the local fish store.

If they are ill, you will see symptoms that could be treated in this quarantine tank with medication instead of treating your main tank.

Improperly Cycled Tank

Your tank cannot be cycled for only 2-3 weeks. Some people use water conditioners, ammonia and bottle bacteria to speed up the process, but a good cycle could take up to 2 months. The ammonia levels will be counteracted by beneficial bacteria that should be thriving.

Sudden spikes can occur in tanks that are not properly cycled. Keep in mind that if there are no nitrates present in your tank, then most likely, it wasn’t properly cycled.

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What Size Tank Do Glofish Need?

Although glofish are small in size, a 5 or 10 gallon tank seems to produce negative results in many cases. Glofish may live longer in 20 gallon or larger tanks. They get scared or stressed in smaller tanks that don’t provide enough territories for them to call their own.

Being smaller than other tankmates means they are constantly on the defense. They feel more comfortable in larger groups of 6 or more, but a smaller tank won’t be able to support that. An overcrowded or cramped tank is sure to give your glofish enough stress to weaken them and possibly lead to their death.

Am I Overfeeding My Glofish?

Your glofish are not picky eaters. They will eat as much you give them. Overfeeding is an issue with fish that are always hungry for more food. If your glofish are dying easily, try a new approach.

Feed your glofish and see how much they consume in 10 seconds. Remove the leftovers and feed them only 1 time a day or once every 2 days.

They will be able to survive and they will produce less harmful waste. Do this for a period of 2-3 weeks and see if this helps to rule out overfeeding as a cause of their sensitivity and susceptibility of dying.

What Can I Do To Prevent Glofish From Dying?

There are so many things to do and so many people giving you advice on keeping fish alive. It’s going to matter how fed up you are about the loss of your glofish.

If you want to take drastic measures, then it’s time to get really serious about keeping your glofish alive. Are you ready for the next level? Here are some tips you can consider that will help you and your glofish:

  • Use multiple filters (ammonia filter, nitrogen reducing filter, etc.)
  • Clean out the tank by scrubbing the decorations and vacuuming the substrate every weekend. 
  • Replace filters once a month.
  • Perform 30% water changes per week.
  • Always keep medication on hand.
  • Do 50% water changes daily if ammonia or nitrites keep spiking. 
  • Add more glofish.
  • Use natural light instead of UV light.
  • Include more plants (Amazon sword, Wisteria, Anacharis, Hogwort).

These tips could get costly, but you’re not messing around anymore. You want your glofish to live up to 3 years with proper care and this is why you’re researching for tips. We can’t guarantee their survival, but we’re digging deep here to help as much as possible.

Can I Cycle My Tank With Glofish?

A fishless cycle with ammonia or bottled bacteria such as Fluval cycle claim to instantly cycle your tank, but most experienced glofish keepers recommend that you should cycle your tank slowly with your fish in the tank for up to 8 weeks.

You will lose some fish along the way, but the beneficial bacteria you gain through this process isn’t easily replaced. Nitrates show that ammonia is being eaten up by the beneficial bacteria. Having no nitrates is a giveaway that your tank wasn’t properly cycled.

Water conditioners remove chlorine, but do not replace what naturally producing beneficial bacteria can do with getting rid of ammonia.

  • Start with 2 glofish, guppies or danios in a 20 gallon tank. 
  • Check water parameters daily.
  • Perform water changes at 25% when there is ammonia or nitrite present.
  • If you’re clear of ammonia or nitrites for 24 hours, then add another fish. 

A fishless cycle will use pure ammonia and fish food instead of live glofish or another fish. It will take about half the time. There is a higher likelihood of sudden spikes if the cycling process is not patiently performed. This is a big reason why many people lose their glofish.


We wish the best for your future glofish to stay healthy and resilient to conditions that cause so many fish deaths. Cycle your tank properly and take your time to introduce your new glofish in your tank. Thank you for visiting HelpUsFish.com and see you again very soon!

Brian Arial

Brian Arial has kept fish for leisure and worked with fish stores for most of his life. He enjoys writing and caring for aquariums and ponds.