Is Fish Tank Water Safe to Drink?

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This could sound like a weird question, especially for novice tank owners who aren’t familiarized with the ins and outs of the issue. First, let’s get the interesting part out of the way. Yes, tank water is generally safe to drink as you will encounter minimal side effects. We’re talking about some gases in most cases, nothing to worry about, really.

But, you might be asking, why would any human drink tank water? Well, pretty much for the same reason people drink pool water – by mistake.

It’s common for people to swallow tank water when starting the siphon and to suck the water through the hose. If you’ve never experienced this issue before, you will trust me.

It’s not necessarily dangerous, but it is unpleasant since tank water isn’t exactly the freshest and tastiest thing you’ve ever drunk.

Should You Drink Fish Water Tank?

You should never drink tank water on purpose. Like the one I’ve mentioned above, accidents are different; these can happen whether you want to or not. But fish tank water isn’t safe for human consumption.

First, it’s dechlorinated since chlorine is deadly to fish. Second, no dichlorination means that the water can host a variety of microorganisms, few of which are friendly to humans. Giardia and Coccidia are just 2 examples out of many.

These organisms are harmless to fish but will cause a variety of health issues to mammals, including humans. There’s no reason to drink your fish’s water. After all, they poop in it.

What Happens if You Drink Fish Tank Water?

In most scenarios, nothing. Fish tank water contains a variety of germs, bacteria, and parasites, but nothing your immune system can’t handle. The problem comes with you having a weaker immune system, making you vulnerable to some of the microorganisms populating the tank water.

Some of these can be quite aggressive, causing fever, headaches, vomiting, etc.

And then you have the ugly part, where certain organisms can infect even healthy humans. Some examples include:

  • Aeromonas – This is an aggressive microorganism that thrives in dirty water and infects a variety of aquatic creatures, causing internal bleeding, among other symptoms. It can also infect humans, leading to diarrhea and blood infections, with children and immuno-compromised adults being the most vulnerable.
  • Mycobacterium Marinum – This bacterium is responsible for causing mycobacteriosis, infecting fish and humans alike. It transmits to humans via infected water and can cause skin infections and internal problems. It eventually goes away on its own but may require medication and even surgical interventions in more severe cases.
  • Salmonella – Everyone has heard of salmonella by now. This is a type of bacteria that usually spreads via consuming contaminated raw food and drinking infected water. The problem is that salmonella-infested fish show no symptoms, making it difficult to diagnose the condition. In humans, salmonella causes vomiting, abdominal cramps, fever, and even more severe symptoms in people with compromised immune systems.
  • Streptococcus iniae – This type of bacteria is generally deadly to fish, and it will also infect humans who mess with the infected water. The main symptom is a skin infection with minimal side effects in the long run. The disease is more dangerous towards people with weak or disabled immune systems.

These are just 4 of the most widespread bacteria that will transmit from fish to humans, but there are more. The bottom line is – you shouldn’t consume fish tank water on purpose.

Can Ammonia From Fish Tank Make You Sick?

Yes, ammonia will make you sick. This is a corrosive chemical that will affect and burn all mucus it comes in contact with. In fish, ammonia poisoning manifests via symptoms like red and irritated gills, respiratory difficulties, lack of appetite, erratic swimming, etc.

In high-enough concentrations, ammonia will burn the fish’s respiratory system, starting with the gills.

Similar symptoms occur in humans. These symptoms are similar to those of pneumonia and may include coughing, a choking sensation, a burning feeling in the chest, light-headed, shivers, etc. If the ammonia concentration is too high, it can kill you. This isn’t something to joke about.

Oh, here’s another interesting fact to mention. You don’t need to drink the ammonia-filled water to get sick. Ammonia vapors can cause similar effects if you empty the dirty water and leave the empty, dirty tank inside the house.

Is Green Fish Tank Water Toxic?

It isn’t necessarily toxic, but it is harmful. To understand why you must first realize what causes the green-water effect. There are several causes for the tank water turning green, including excessive lighting, poor maintenance, and even constant overfeeding of the fish.

All these issues will lead to algae overgrowth and allow for a dangerous build-up of harmful bacteria. The result is visible with the naked eye – the water will gradually turn green, making the environment seem murky and unclean.

Green water isn’t typically harmful to fish, so long as you treat the causes soon. If not, your fish will experience breathing problems and face dangerous levels of ammonia and nitrates.

The latter chemicals will also affect you if you decide to have a gulp of the tank water. For whatever reason.

If you do need to use a siphon, try to work your way around using your mouth to start it off. Or, at least, be wary of the risks and try not to swallow any water.

Can Cats Drink Fish Tank Water?

If you have cats, prevent them from drinking from the tank. They certainly can, and they certainly will if given the opportunity, but they shouldn’t. Fish tank water contains a variety of parasites and bacteria that could infest your cat, leading to a variety of health problems.

Use a lid to cover the tank, especially since, in many cases, cats also decide to have a go at those little colorful things swimming under the water’s surface.

And since we’ve touched upon this point, you should never feed your cat sick, dying, or dead fish. Aquarium fish are generally filled with parasites and bacteria, which, while relatively harmless to your fish, can hurt your cat.

Can Parrots Drink From Fish Tank?

The answer is identical to the one regarding cats. No pet, human, or any other creature should drink from the tank water. Fish have numerous parasites that could infect other animals with nasty consequences.

If you have nosy pets around your home, use a lid or cover the tank with something.

It’s also worth mentioning that parasites aren’t the only threat, but medication as well. If you’ve medicated your fish recently, any pet drinking the water may often experience severe health issues.


Drinking fish water won’t kill you, but why take the risk? You should never drink it on purpose due to the high risk of infections and diseases that you could contract.

You should also try to minimize the frequency of accidental swallowing of tank water and do the same for your pets.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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