Can I separate my two goldfish? One would still be with other fish.

Thanks for reaching out about Corn. Despite what most people think, fish are subjected to stressors and are social organisms. Whether the goldfish and danio are bonded or not, can not comment. You could provide a heater for the goldfish also, as they do better is kept at a more consistent temperature. As for other fish, goldfish and tetra families do pretty well, although goldfish have been known to occasionally eat smaller fish. Good luck.

This could be due to having a tank that is too small. 6 goldfish in one tank poses several potential issues. Ideally, 1 fish should have a 20 gallon tank with an additional 10 gallons provided per extra fish. This would mean they should be in at least a 70-75 gallon tank. The reason being goldfish produce a larger than average bio-load (wastes) that can quickly overwhelm a small tank and filter. Poor water quality can lead to stress and infection as well as behavioral issues. Depending on their sizes, the present tank could be overstocked leading to bullying and fin nipping. Check the water quality and chemistry. Use a home test kit or submit a water sample for testing. Most pet stores will do this for free or for a small fee. Aim for an absence (0 ppm) of ammonia and nitrites with a nitrate level of 20 ppm or less. Perform partial water changes, if indicated, to stabilize chemistry and maintain or improve water quality. Use only aged or conditioned water that is temperature matched to prevent further stress or shock. Goldfish are cold water fish and do best between 65 F and 72 F (18.3 - 22.2 C). Make sure the filter is rated for at least twice the volume of the tank. If possible, separate out the aggressive goldfish to a different tank to prevent further bullying and injury.

A pet store won't be able to take them due to disease risk to their stock, regardless of how healthy they are. You could advertise them as free to a good home on a buy and sell site. You can't just put them into a body of water as they wouldn't be used to it and would not survive. You don't necessarily have to keep them in a tank, even a large plastic box/ bucket would do.

Thanks for reaching out. Oscars are fairly aggressive and will try to eat each other, depending on their size. Be prepared to separate if needed and monitor interactions. Keep them well fed and provide plenty of hiding locations. Good luck.

Thanks for reaching out about your fish. Typically, most recommendations are 1" of fish per 3 liters of water. The better the filter system, the better the water quality and the more biomass can be handled. Remember, fish grow and therefore the biomass will increase. Good luck.

Gold fish can make great fish but they can live up to 25 years and require a large tank that may need to be upgraded if they grow too large. Do get at least 2 fish. Here are some links which may help: https://www.petcoach.co/article/chewing-in-puppies-how-to-control-it/ https://www.aqueon.com/information/care-sheets/goldfish https://www.hartz.com/how-to-introduce-new-fish-into-your-aquarium-tank/ I hope this helps and congrats on your new pets!

Male Bettas should be housed alone as they can be quite aggressiv, especially to other male Bettas. He's not lonely. He is likely seeing the fish and displaying at them in the hopes that they will swim away. Watch Thomas closet and you will see him flaring his gills and fins out as he stares them down. It looks quite comical, but to him, it's serious business "guarding" his territory.