Is a 30 gallon Tank big enough for a young chinese water dragon?

Really it depends on its size. If he is rather small and has space to climb and jump and hide and at the very least a large bowl of water in there to swim/soak, then yes for now it is ok though not ideal. Keep in mind they grow rather quickly so even if he is fine right now, he will be larger and more than likely he will outgrow the tank in just the next couple of months if you have the proper UVA and UVB lighting that he needs and if he is fed well. I would definitely start building his large enclosure now or convert an unused space into his, such as a closet, bathroom, or unused bedroom. I converted our large master bathroom into an enclosure for my two female water dragons and it is about 20 feet long x 9 feet tall x 5-6 feet deep. The minimum space for a water dragon enclosure is the size of a large refrigerator. However, it is recommended to be at least 6 feet tall x 6 feet wide x 3-4 feet deep. These lizards love to climb, jump, and swim so make sure you offer him lots of space to do each when you are creating his new enclosure. Here's a great website that you can check out when you have some time. Good luck.

http://www.triciaswaterdragon.com/dragoncr.htm

PS- A 55 gallon tank is not large enough for an adult water dragon. It may be long, but it does not offer enough space for them to climb or jump. Just because they fit in the tank semi-comfortably, does not mean it is appropriate for them. It would be for a bearded dragon, but water dragons NEED space to be active and climb high. A happy lizard is a healthy lizard. More is always better for these guys.

I have one and he's in a 40 gal. because he's only a foot head to tail , a 30 gal. would work but for a very little time, he soon will grow really big and will need a cage the size of a large refrigerator when he is an adult. I didn't know what I was getting in to when I got one, but if you really want one and can burn a lot of cash the chinese water dragon will be perfect

When he is young, that is a perfect size. But when he is full grown, you will need a 55 gallon tank for him. Have fun watching him grow!

for a young one yes but he needs alot bigger...