If you’re new to keeping goldfish, you may be wondering whether they can live in normal tap water.
Lots of beginner goldfish keepers think they can simply add water straight into their tank along with their goldfish.
However, if you want your goldfish to live a long and healthy life, this is definitely not a good idea.
Goldfish shouldn’t live in untreated tap water
Goldfish cannot live in untreated water straight from the tap. This is because tap water contains chemicals that are bad for your fish. And, even worse, can kill all of the ‘good bacteria’ in your tank.
Good bacteria develops through a process called cycling, which we talk about in more detail here.
Essentially, cycling involves cultivating bacteria that will take your goldfish’s waste (ammonia) and turn it into less harmful chemicals.
It’s vital that you maintain this delicate eco-system of good bacteria. But adding tap water can completely destroy it. The chemicals in tap water can kill some or all of the bacteria. This stops the bacteria from processing ammonia, which causes ammonia poisoning and seriously harms your fish.
What about water changes?
You might be wondering – “hold on, if I can’t add tap water, how do I do water changes?”. And of course, you do still need a regular routine of water changes.
While you shouldn’t add tap water straight into your tank, this doesn’t mean you can’t add it at all. You just need to treat the tap water first and only add small amounts at any one time.
We recommend a product called Seachem Prime for treating water. Each week, you can remove up to a third of the water from your tank and replace it with treated tap water. Just be sure to follow the instructions on the bottle.
Finally: You should never wash your filter, filter sponges, decorations or substrate (such as gravel) in tap water! These are the prime living spaces for that good bacteria we mentioned. So keep them in tank water at all times!