Why are my goldfish suddenly scared and darting in their tank?

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.

Check water chemistry first. Use a home test kit or submit a water sample for testing. The local Petco may do this for free or for a small fee. Aim for an absence ( 0 ppm) of ammonia and nitrites with nitrates at 20 ppm or less. Perform partial water changes, no more than 30% at a time, to stabilize chemistry and/or to improve water quality. Use only conditioned water that is temperature matched to prevent stress or shock. Check water temp as well. Any of these can drive a fish to the surface. The "flashing" (darting about) can be due to infection (bacterial, fungal or parasites). Consider a broad spectrum antibiotic or an "all in one" product to treat multiple infections. Look in the Aquarium section of the local Petco for options. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.

Did you change any of the plants or other features in the tank? That could be confusing him. It could also just be due to stress. Did you take him out while you changed the water or did you leave him in? Taking him out is recommended but it can still be stressful for him due to all the moving. Did you do a partial water change or a full change? Since I am not sure of what your procedure was it is hard for me to comment. I suggest you refer to this article about how to properly change the water to make sure you are doing it correctly. If you still have more questions please feel free to post again. ( https://goldfisho.com/goldfish-tank-water-changes/ )

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!

Thanks for reaching out about Goldie. There are two concerns here: (1) not apparently eating and (2) high ammonia. For the appetite, try to note if there is feces. If feces, then eating. If appear getting thinner, then not eating enough. For the second problem, this is probably new tank syndrome, and not allowing the biological filter to establish. Water changes are needed to bring down the ammonia as that is toxic to the fish and damaging to the gills. Probably the reason for the frantic swimming. Good luck.

Thanks for reaching out about Kirky and including a photo, although the photo is out of focus. Swimming to the surface and gulping air is typically and indication of gill disease. Gill disease can be caused by poor water quality, bacterial infections, gill parasites, and metabolic disorders. First, check water quality for pH, ammonia, nitrites and nitrates. Correct problems. Make sure to treat tap water for several hours prior to adding to the tank. If water quality is correct, a veterinary visit for assistance in a diagnostic/treatment plan. A gill clip can be examined under the microscope to determine parasitic or other gill disease. Antibiotics added to the water typically cause more problems than benefit, altering biological filtration. Good luck.

Hi, and thanks for your question. This is a quite concerning presentation and it is likely to be related to water quality. Begin by submitting a water sample for quality testing. Most pet stores will do this for free or a nominal fee. Clinical examination should always include a water quality check, even if you have done so already. Water testing should be performed with a quality test kit, measuring NH4, NO2 and NO3. High ammonia levels, PH imbalances may be responsible for these signs. Oxygen concentration and quality of the filters should be determined as well. If water quality is good and there are no major imbalances, your fish should get examined to look for any sign of bacterial/fungal infection and eventually water should be treated. Hope this answer was helpful, but please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further. If this answer was helpful please let us know, this will be used to improve our service!