1. Temperature: Goldfish Prefer Cooler Water than Most Other Kinds of Fish
Tropical fish (such as Cichlids, loaches, tetras and others) need to live in temperatures that would be too toasty for goldfish.
Goldfish prefer temps in the 70 to 80 degree F range with changes from season to season.
Tropicals don’t require periodic cold spells, which help goldfish to shed their excess fat. In fact, colder water may harm their health.
One party would end up compromised, so it just isn’t fair.
2. Aggression: Your Goldfish Can Get Picked on
There’s no doubt about it:
Getting picked on isn’t fun.
For goldfish, it can be very stressful.
Putting other types of fish in with your goldfish all too often leads to bullying or injury. Your goldfish may end up spending its days hiding in terror from its persecutor.
Algae eaters (such as the plecostemos) are responsible for a large number of goldfish injuries on a regular basis, as their suction cup mouth can fix on the side of the goldfish and chew away at their tasty slime coat.
Want to know the worst part?
They typically do their dirty deeds when nobody is around to watch them.
This leads goldfish owners to think their fish are sick when suddenly they wake up to a large red sore on their goldy’s side.
Koi are notoriously overbearing towards their smaller fancy cousins and should never be housed in the same tank with them. They also get much, much larger than goldfish and do best in ponds.
If this happens in your tank, don’t blame the bully. The fish isn’t being mean – it is just doing what it naturally does.
Right now, if you have your goldfish in with them, get them out immediately.
You may have to find another home, or start up another tank (we’ll get to that later).
3. Your Other Fish May Get Digested by Your Goldfish
It’s a fact:
A goldfish will eat any fish that fits in its mouth.
So while it is still young your other fish may be okay…
… Until after another year or so, when the goldfish has doubled in size.
One day you might look in the tank and think your other fish went *poof* into thin air.
Since they do it with their own babies… they probably don’t think twice about turning their tank mate into sushi!
Bonus Reason: Goldfish Have Different Diet Requirements than other Species
It’s a fact that goldfish require a large amount of vegetable material to keep their digestive tract working correctly.
Too much of a high protein diet can lead to swim bladder troubles.
The other type of other fish you get will probably have much different nutritional requirements than your goldfish.
This brings us to the next question:
So What other Fish Do You Put with Your Goldfish?
The good news is, you don’t have to have one isolated little goldfish as the only inhabitant of your beautiful aquarium.
(That is, if it is large enough).
Goldfish are community fish and get along great with other goldfish the majority of the time under normal circumstances. Some people think they even form bonds with each other as lifelong friends.
There are some things to keep in mind, which are:
1. The size of the fish
It isn’t a good idea in most cases to put really small or young goldfish in with a “Shamu” sized buddy.
One will end up getting all the food, and the other one going hungry – which can lead to malnourishment.
When in Doubt, Always Remember that Less Stress is Best!
Diversity in the tank is interesting and important, no doubt.
But so is the happiness of your goldfish – and your sanity.
Many times it’s just a bad idea to add more fish into the tank PERIOD because there just isn’t enough room to support the tank’s inhabitants.
This leads to all kinds of problems…
… Which can include having your fish feeling very stressed from overcrowding.
I think we all want the best for our pets.
But don’t lose hope!
You can always keep a separate community tank if you absolutely must have a variety of other types of fish. That way you won’t have to deal with any of the problems that come with mixing goldfish with other kinds of fish.
Here’s a tip:
Just be sure you don’t go too crazy, as too many tanks can make you stressed out if you are too busy to maintain them all. 😉
If You Just Have to Have An Algae Clean-up Crew, Here’s an Option…
So algae eaters aren’t a good fit for goldfish.
There’s good news:
Mystery snails are a good choice for goldfish, as they are relatively hardy and quite peaceful.
Be sure you quarantine any snails you get before adding them to your tank, as you don’t want them to bring in diseases from the pet store.
Some Final Thoughts
There have been and always will be people who claim to have success mixing different types of goldfish tank mates.
Granted, there are times when it does seem to work out every so often.
These are the exception, NOT the rule – in my humble opinion.
Things may seem to go “swimmingly” for a while…
But sooner or later, 99% of the time you will run into trouble.
One thing is for sure:
When it comes to goldfish keeping it is always better to be safe than sorry!
The risk of injury or even death to any of your tank’s inhabitants just isn’t worth it.
You don’t want to make any fatal mistakes with your beloved pet, which is why we wrote the complete guide to goldfish care, The Truth About Goldfish.
It has all the answers you will need for keeping a thriving, harmonious, disease-free goldfish aquarium.