Please note: this post is not targetted at anyone and has the interests of the fish at heart.
I just want to clear up some misconceptions about keeping goldfish and bettas together, because it is unacceptable and involves compromising the ideal conditons for both fish. I might offend some people with this post, but no serious goldfish keeper mixes these two species, or ever mixes tropical with coldwater. Here are some good reasons to never, ever, ever place the two together, even if it does work out for a while. Like most aspects of fish keeping, something that works temporarily does not tend to work long term when mixing incompatible species.
- Goldfish are a social species and require the company of their own species in the long run. Other species of fish make poor replacements, and over time, neurotic stereotypical behaviors may be observed.
- Bettas are a solitary species that tend to be stressed by the presence of other fish. They may act aggressively, or may patroll and defend an area of the tank against tankmates to the point of physical exhaustion.
- Goldfish have a notoriously high waste output and parasite load. Most tropical fish can not remain healthy in the amount of waste goldfish produce, and are sensitive to parasites that goldfish carry but are not seriously affected by. Bettas, with their long fins, are very sensitive to water quality, making goldfish and exceptionally poor choice for a tank mate.
- Goldfish are active fish that require water with high aeration, a fast current, plenty of open swimming space, and cool temperatures. They also prefer a higher pH and hardness.
- Bettas do best in low/no current, low aeration water conditions, high temperatures, and require plenty of hiding and "perching" spaces to feel secure. They prefer an acidic pH and minimal hardness.
- Fancy goldfish need a MINIMUM of 20g to survive to maturity - think 20 YEAR lifespan at 8+ inches in length regardless of the type! Common goldfish can grow to 24" when properly cared for, and can not be kept in anything but a pond at maturity. Remember, inch per gallon does not apply to goldfish because of their waste output; they need anywhere from 3-5x's the gallons per inch of a tropical fish.
- Bettas are most comfortable in tanks 10g and under due to their territorial drive to patrol and may become stressed or exhausted trying to swim in larger tanks, especially if the presence of other tankmates inspires them to patrol.
- Goldfish get huge and eat anything that fits in their mouth.
- Bettas are one of those things that fit in a large goldfish's mouth.
- Goldfish are omnivores require a diet of fresh leafy greens and veggies, small amounts of fruit, and a high quality pellet (not flakes; flakes can cause impaction and SBD and should especially never be fed to fancies). They are food hogs and will happily chase away or injure fish who come between them and their food.
- Bettas are carnivores and require a diet of high quality pellet (for carnivores, not goldfish!), hopefully with some frozen or live foods to promote good health. But goldfish will happily eat a betta's food and prevent them from eating.
- Goldfish are known to be fin nippers as they'll try to eat whatever they can get their mouth on. Commons especially are fast moving and can easily outswim and chomp on a VT.
- Bettas are also known to be aggressive and can injure or kill smaller fancy goldfish since these species are notoriously poor swimmers.
I could go on forever with this, but hopefully you get the idea. There is no good reason or justification to mix a large, social, high current, high aeration, coldwater omnivore with a small, territorial, aggressive, low current, low aeration, tropical carnivore! Goldfish belong with goldfish, bettas belong alone or with suitable tank mates, and coldwater never belongs with tropical.
The goldie you have might be a ryukin or a ryukin mix.
Goldfish are mucky little devils unlike my bettas who are very houseproud.!
In this case we are also apparantly comparing a fancy goldie and a common goldie.
