Betta fish and goldfish are the favorite choice of pet fish for many aquarists, especially kids. So, you might be thinking about how cool it would be to have both species living together in your home tank.
But can bettas live with goldfish? Betta fish have a pretty fierce reputation, whereas goldies are super-chilled out. So, would an arrangement for the two to live as tankmates be a marriage made in heaven or a recipe for disaster?
In this guide, we answer those questions and explain why goldfish and bettas might not be the happiest of bedfellows after all.
Goldfish and betta fishes
The iconic goldfish has arguably been the favorite choice of kids’ pet for decades, joined more recently by the betta fish. Both fishes are beautiful to look at and are relatively easy to care for, certainly more so than a cat or a dog. However, these are two totally different species with different requirements when it comes to their care.
Let’s take a closer look at bettas and goldfish to find out why they are so different.
All varieties of goldfish are distantly related to a species of Prussian carp, which are found primarily in Central Asia. It’s thought that there are approximately 125 goldfish varieties, which have all been created by crossbreeding and captive hybridization. There are no wild species of goldfish, unlike Placat betta fish, which are still found living in nature.
Wild carp inhabit slow-moving waters in ponds, rivers, lakes, and ditches, just like betta fish in nature. Also, pet goldfishes often find themselves confined to a small bowl or nano aquarium, which is an unsuitable habitat for these potentially large and dirty fish. Goldfish need a spacious tank with a very efficient filtration system to remove the vast amounts of waste that the fish produce. Also, all varieties of goldfish can grow to a fairly large size, and that cute two-inch Oranda you bought home will quickly morph into a six-inch stunner with gorgeous flowing fins.
Unfortunately, you’ll often see betta fish in a tank that is very small and has no filter system. However, wild bettas do like to establish territories of several feet square, so you can see that a tiny bowl is not suitable for them at all.
Unlike the artificially raised goldfish, bettas do exist in the wild, although not in the fancy, long-finned varieties that are so popular with hobbyists and that you see for sale in fish and pet stores.
Bettas belong to the Osphronemidae tropical fish family that originates from southeast Asia and also includes another popular aquarium fish species, gouramis. There are an incredible 73 varieties of bettas, the majority being bred in captivity and heavily crossbred to produce the glamorous finnage and beautiful colors that are so coveted by enthusiasts.
Wild bettas live in small populations centered around the Chao Phraya and Mekong river basins in Thailand. Here, the fish live in slow-moving, shallow bodies of water, rice paddies, marshes, and ditches.
All bettas are termed “labyrinth breathers.” That means that the fish have a specially evolved labyrinth breathing organ that allows the betta to gulp air at the water surface. Much of the betta’s habitat is low in dissolved oxygen, and the labyrinth organ allows the fish to survive when water conditions are poor, typically during the dry season. Unfortunately, that has led people to believe that bettas are happy in tiny bowls without any filtration, which is not the case at all.
In fact, according to research that was undertaken by Adelphi University, the betta fish requires at least a two-gallon aquarium with a good filter system, heating, and lighting to remain healthy and thrive. Like goldfish aquariums, betta fish tanks must be cleaned regularly to maintain the optimum water conditions that these fish need to be happy.
Are betta fish aggressive?
In a word, yes! Betta fish are not also known as Siamese Fighting fish for no good reason!
Male betta fish are extremely territorial, defending their adopted patch vigorously to all-comers, even a placid goldfish. In Thailand, back in the 1800s, people raised wild betta fish specifically for fighting. Two fish would be pitted against each other, and spectators would wager on which fish would win the battle. Even the King of Siam was a keen owner of fighting fish and supported licensed betta fights.
Modern bettas are no different from their “Placat” ancestors. If a betta fish catches sight of his reflection in the tank glass or in a mirror, he will flare at the perceived intruder and even attack it.
At the other end of the aggression spectrum, we find the placid goldfish. Goldies are the chilled-out dudes of the aquarium, enjoying the peaceful company of their own kind, mostly keeping to themselves and spending much of their time foraging for scraps of food or digging up plants.
That said, some varieties of goldfish can be fin nippers, and they also grow much bigger than betta fish. Also, the betta splendens are not built for speed and are somewhat weighed down by their flowing finnage. Unfortunately, a speedy comet-type goldfish would easily outswim a betta and could inflict considerable damage on its fins.
The bottom line: Place a fin-nipping, fast-swimming goldfish in the same tank as a highly territorial and aggressive betta that views any fish with bright colors as a possible threat, and you’re asking for a full-scale war to break out in your aquarium!
And don’t let the betta’s small size fool you. Betta fish will take on fish that are much larger than they are if they think that their territory is under threat.
So, we know that the personality types of bettas and goldfish don’t gel. But what about environmental conditions?
Goldfish live in cold water, ideally in the temperature range of 68o and 74o Fahrenheit. Bettas, on the other hand, are tropical fishes, and they must have warm water between 75o and 86o Fahrenheit if they are to survive.
A betta fish will suffer from temperature shock if the water temperature in the aquarium falls below 75o. Even if your betta isn’t shocked, his metabolism will run more slowly, your pet will stop eating, and he will become very lethargic. Because the fish’s circulation is not functioning correctly due to his inactivity, he may develop diseases, including fin rot. So, you can see that keeping your betta fish in a cold tank is asking for trouble and could ultimately kill your pet.
Goldfish can also get sick, but if the water becomes too warm, rather than too cold. So if the water temperature sneaks over 75o, your goldfish could be in trouble.
So, the primary reason why goldfish and bettas are not compatible tankmates is that they need totally different water temperatures to survive.
Water is described as hard or soft, depending on its mineral content. Fish do use the minerals in the water as part of their nutritional requirements, but different fish species have different water hardness tolerance and preferences.
So, betta fish need soft water that contains hardly any calcium. The lower the levels of calcium, the lower the water pH level will be, and bettas need a water pH level of close to 7.0 to be happy.
However, in contrast, goldfish prefer tank water with a higher calcium content, which, consequently, has a higher pH level, ideally between 7.2 and 7.6.
Goldfish are much larger than bettas, and they do produce an awful lot of waste. Goldfish don’t have stomachs, so everything that they eat passes straight through the fish and into their aquarium. So, it’s essential that your fish tank has an efficient, mature biological filtration system that can cope with the waste products and control the Nitrogen Cycle. You’ll also need to carry out partial water changes every week to keep the levels of ammonia, nitrites, and nitrate under control.
Betta fish are extremely sensitive to ammonia in the water, and they can quickly fall victim to ammonia poisoning, and that can be fatal to your picky pet. Also, although goldfish tolerate frequent partial water changes, bettas are stressed out by that, leading to a compromised immune system, which exposes the fish to attack by diseases and parasites.
When it comes to water movement and flow rate, a tank with goldfish living in it does need a fairly strong flow to ensure that the water circulates through the filter system at a good GPH (gallons per hour) rate to keep the environment clean.
Unfortunately, a strong flow rate is exactly what your betta fish doesn’t like. Fancy varieties of betta fish have long, flowing finnage that looks stunning but is a distinct handicap for swimming. A comparatively tiny betta encumbered by heavy fins will struggle to swim in fast-flowing water. Again, living in an environment where he can’t swim properly and is continually buffeted by the water will cause your fish a lot of stress, which could expose him to diseases.
You could fit a baffle to the filter outlet to restrict the current but keep the flow rate or perhaps use a sponge filter to suit your betta fish, but a sponge filter will never handle the quantity of waste that the goldfish generate.
Tank size and decoration
Betta fish are small, growing to just 2 inches or so at maturity. So, your betta can happily live in a 10-gallon tank and still have plenty of space to be happy. However, some varieties of fancy goldfish can reach up to six inches or more when fully grown, and the more streamlined types can make eight inches in length or even more.
Tank décor that suits goldfish doesn’t necessarily work for a betta. Betta fish prefer an environment that has lots of dense planting where they can rest and hide. Bettas also like caves in which to hide and explore and plenty of driftwood and other ornaments that they can investigate while patrolling their territory.
Goldfish can be very destructive, where plants are concerned, uprooting them while foraging through the substrate for scraps of food. Fancy goldfish are notoriously poor swimmers, and too many decorations and bushy plants obstructing their swimming space can spell disaster and even lead to injuries.
What about a temporary arrangement?
In theory, you could put your betta fish and goldfish in the same tank for a day or two in an emergency situation. For example, if your betta tank heater failed, you could put your betta in your goldie tank while you get a replacement heater.
However, we recommend that you use a quarantine tank as a temporary home for your betta, rather than stressing him out by placing him in an unsuitable environment.
At the end of the day, bettas and goldfish simply don’t mix. They don’t share the same requirements for water conditions, tank size, and tank setup.
So, can betta fish live with goldfish? The answer to that question has to be no. Sadly, although these two species would look great together, there are just too many things that goldfish prefer, and bettas hate for the two to get along as permanent tankmates. In theory, you could perhaps have a betta fish live with a fancy goldfish for a day or so, but that would have to be a very temporary arrangement.