Why are my danios chasing and hiding? Are they fighting or stressed?

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.

The goldfish can get very big and may require a significantly larger tank as they grow and grow. As a rule of thumb, you need 1 gallon of water per inch of body length of fish. So if you have three 1 inch fish, you will need 3 gallons of water. I suspect you are at your max already in the smaller tank. Just so you know, most people do not have goldfish in tanks with tropical fish. You may consider getting two tanks One for your cold water fish like the goldfish, and one for your tropical fish that require a warm water temperature. For the goldfish I would suggest a minimum of a 20 gallon tank. For the Danio, I suggest to get a few more of these as they are schooling fish and a 10 gallon would be just fine. I hope this is helpful and please feel free to post any additional questions.

They need a much larger tank. A 20 gallon tank (properly cycled) suffice for several months. When full grown, a minimum 55-60 gallon tank with adequate filtration will be necessary for healthy fish. For now, maintain water quality via filtration and weekly partial water changes. These fish do best at temps between 65 F and 72 F but can tolerate colder temperatures as long as temperature swings are not too rapid.

GloFish are schooling fish. They do best in groups of 6 or more. If you have just a few, they may be stressed which can cause aggression. Check the water parameters since an imbalance in chemistry can cause stress as well. You can use a home test kit (one with liquid drops, not test strips) or submit a sample to you local pet store or aquarist. Most will perform water testing for free or for a nominal fee. Ideal parameters measure 0 ppm (parts per million) ammonia and nitrites with nitrates at 40ppm or less. pH of the water should be between 6 and 8. They are cool water fish, so aim for a water temp between 65 F and 75 F. Hopefully, this will help. The other option you have is to remove the aggressor. You can request a consultation to discuss the situation and set up in greater detail or if you have further questions or concerns.

Thanks for your question about your fish, and congratulations on your new family members! I didn't see how recently the tank was set up, but there are a couple of things that could be going on. I would start by checking your water quality - any abnormalities in water quality can make fish have abnormal behaviors, and the water looks a bit murky in the photos you provided. There may be parameters that need to be addressed depending on what you find. If you do not have a water quality kit, they can be purchased at the pet store or an aquarium store, or you can take a sample of your water in for evaluation to these places as well. Some will charge a small fee for this service, just so you are prepared. Also, with recent tank set ups, it can be stressful for fish as they are in a new habitat. I would recommend keeping the light on for only a few hours per day to start, as the bright lights can be shocking for them (since fish don't have eyelids). Gradually you can increase the length of time that the lights are on so that you reach a cycle of 10-12 hours of light and 12-14 hours of darkness for them. I hope this gives you a place to start, and I wish you and your mom the best with the new pets!

There are several species of Tetras and sexing them can be tricky or downright difficult. Neons are the easiest. Look at the neon line along the body. If it is straight, you have a male. If there is a slight curve, you have a female. In other species, it isn't as easy. Females are generally rounded and fatter. Males are longer and slimmer. Male Danios have more vivid and shiny colors than females. Both have yellow between the stripes, but males are more vibrant. Male Danios will also be longer and slimmer while females will be shorter and "thicker". If they spawn, you can leave the eggs and adults in the main tank. The adults will eat the eggs...or fry (baby fish) if they hatch. You can also vacuum the eggs out and discard them.

Check the water chemistry and water temperature. If it is a new tank, it may not be properly cycled and could be undergoing and ammonia or nitrite spike. Either can drive fish to the surface or to one area of the tank. Submit a water sample for testing or use a liquid master test kit at home. Aim for 0 ppm ammonia and nitrites with nitrates at 40 ppm or less. Water temp should be in the mid 70s F. Perform a partial water change (30%) if necessary to stabilize chemistry and maintain water quality. Use only aged or conditioned water that is temperature matched o prevent stress or shock. Survey the area around the tank to rule out negative stimuli such as bright/direct light or loud noises/vibrations. These can also stress fish and cause them to move as far away as possible. Make sure the tank is large enough to support 8 guppies. Overcrowding can cause stress and aggression. Lastly, provide plenty of cover in the form of live or artificial plants. Guppies prefer cover and guppy fry (babies) need it or they will get eaten.