I've recently got a pair of goldfish and put them in a bowl. I'm trying to keep them happy by feeding them all the natural thing they eat in the wild (and they are loving it too).
It has been 4 ~ 5 days and things were going fine, until I got them a little bulb to keep them warm and light up the bowl a bit. But, after around 2 hours from the moment I switched the bulb ON, the fish would come to the top, pop their mouth out of the water surface a bit, and gulp air, then they would go down and release bubbles.
Initially, I thought, that due to low oxygen and high impurity rate in the bowl, they are gulping air from the top and immediately changed the water. But, again when I put the bulb back on, they started coming to the top releasing bubbles.
I don't know if they are doing this to get more heat (as it's a bit cold these days here) or they are just feeling good doing this... Please help me as soon as possible... :(
Both of my fish are 2.5 inch (7.5 cm).
I change their water every 3 days.
When the bulb is removed they discontinue this behaviour.