Water Dragon noise

Question
My juvenile water dragon (unsure of the sex) has been making a strange noise like croaking of a frog. He/she opens his/her mouth like a gasp and then pulls in his/her chest and squeezes out a quiet croak-like noise. I have no idea what this is. He/she also will not eat crickets or veggies but will eat worms. I don't know what to make of this since I have never had a water dragon before. One last question, I have heard lots about vitamin supplements and calcium supplement; I have the calcium one but unsure about the vitamin supplement (does he/she need it?).

Answer
 Surprisingly enough, dragons from the Agamid group can produce a froglike noise, but I would have the dragon checked for a respiratory infection just in case. He could be stressed from a tank that is too small.  They need a huge amount of floorspace, and 1/3 of that should be a swimming area. Get him checked by a good herp vet just to be sure.  If you don't have one, go to www.herpvetconnection.com.
He should be eating a good salad.  Try good calcium rich greens like collards, dandelion greens, turnip greens, mustard greens, mache and arugula.  Zophoba worms are good as long as they are properly gutloaded with a nutritious bedding like from Cricketfood.com.
 I prefer Rep-cal Calcium and Rep-cal Herptivite for supplements.
 Check your temps with a good digital thermometer, he/she may not be eating well due to a lowering in temperature.  I don't know where you are but it got cooler in NY rather quickly, I had to run out and buy a lot of higher wattage bulbs for all my scaley kids to get their temps back to normal!
 You didn't mention UVB lights, If you have had your for about 6 months, it's got to be replaced.  UVB production decays to nothing in that time.  Get a Reptisun 10.0, at least 36" to provide enough UVB to help him metabolize his food.