Do goldfish bite?
Goldfish have teeth (called Pharyngeal teeth) but they are at the back of their mouth so getting bitten is not likely to happen. If their mouth was to come in contact with your finger or hand, the most they could do is suck or 'kiss' it. Remember, goldfish are very small and so their teeth will only be tiny too! Any contact would be painless.
How often should you clean your tank?
You should change the water in your tank once a week, which will keep ammonia levels down, help to increase oxygen in the tank and also cleans away any waste that has built up from the week before.
Can more than one goldfish live together?
This will depend on the size of your tank. Ideally one goldfish should have at least 10 gallons (approx 45 litres) of water to live comfortably. If you wanted to give him a friend you would need to increase the size of your tank by adding another 10 gallons — this ensures that there's enough oxygen for each fish.
You will need to be careful when deciding on whether or not to get your goldfish a new companion, as combining different goldfish varieties can lead to problems. These problems can be anything from goldfish bullying, stress, and the smaller / slower goldfish may not feed properly. It is essential that you keep goldfish of the same type, size and speed in the same aquarium.
Do goldfish like being handled?
Your goldfish may swim towards your hand if you're in the process of feeding them, but you should avoid touching them at all times. They may be comfortable to swim around your hand or finger, and take food from you but try not to let them touch you. Even the slightest of touches against the goldfish's skin can cause damage. The slimy coating that protects them from bacteria and toxins is there for a reason, any any contact could potentially upset this which in some cases can be life threatening to the fish.
By all means interact with your goldfish, and play with them (sensibly) — just avoid brushing against their skin and scaring them.