They could be seeing themselves in the reflection of the glass of your tank, but since goldfish do not have the capacity to recognize themselves in a reflection they think it is another goldfish and attempt to swim towards it.
It has nothing to do with having a short memory span as the previous answer said, because goldfish actually have a long-term memory span of about three months.
They may try to get some oxygen XD
Yes
It is important to remember to put things in a goldfish tank, even goldfish get bored. Some of my suggestions for tank decor are artificial plants and a "hidey hole" for your goldfish.
You should not have goldfish and platies in the same tank ever.
depends, can a ten gallon tank live in a goldfish
getting more goldfish in your tank
Regardless of the type or size of goldfish the minimum acceptable size of an aquarium for a goldfish is 30 gallons. Buy a tank that is at least 30 gallons if you plan to have goldfish. You can comfortably fit 3 goldfish in a tank this size but no goldfish in a tank any smaller. Goldfish are essentially pond fish and need lots of space to swim; they will not thrive in a small aquarium.
Either a tank or pond of at least 30 gallons is a suitable environment for a goldfish.
no. you should have 10gal of water per goldfish. you shouldn't have goldfish in a 5gal tank at all. they are huge waste producers
Yes, goldfish are very messy. Goldfish need 10 gallons per fish, you actually need a 20 gallon tank or about a 70 liter tank for 2 goldfish. But the small tank will do while they are small, you will need to eventually get a larger tank.
No. A one gallon tank is not appropriate for a singular goldfish much less multiple. A ten gallon tank is the bare minimum for a singular goldfish and breeding would require a tank of twenty gallons or more. A one gallon tank cannot handle the chasing that proceeds goldfish mating nor maintain a water quality that is suitable for raising goldfish fry.
glass tank