I bought two gold fish (Gonzo and Princess, my girlfriend named the latter), they are in a simple bowl with no air pump. The pet store suggested I buy oxygen tablets (at the same price of the two fish). All I do is pop one in every two days. It takes about 4hours to dissolve, slowly releasing bubbles. How do they make it, whats it made out of, and do they work?

I am currently babysitting three tankfuls of assorted tropical fish while my daughter is away on holiday. They seem to be very active all the time. Do they ever sleep, even though they appear to have no means of closing their eyes?

On a related theme, do captive fish appreciate they are safe, and does that influence their behaviour?

Catherine Spalding, Bristol, UK