Hi, I have a problem with one of my goldfish. It can't seem to balance itself and is constantly floating on the top of the water. When the light is off it simply lies there still and doesn't move. When the light is turned back on it tries to swim down, but it's like it's full of air or something. Can you help?

Test Results for the Following:
Ammonia Level?don't know =/
Nitrite Level? ''
Nitrate level? ''
Ph Level, (If possible,KH and GH and chloramines)? ''
Ph Level out of the Tap? ''
Tank size (How many Gals) and How long has it been running? 3ft x 12 inches x 18 inches (sorry)
What is the name and size of the filter/s? Fluval size 3
How often do you change the water and how much? one third of tank every week
How many fish in the tank and their size? 6 one large one (the ill one) 5 inches. three medium ones all about 2 1/2 inches 2 small 1 1/2 inches
What kind of water additives or conditioners? Anti-chlorine adittive Tetra Aqua
Any medications added to the tank? No
Add any new fish to the tank? One recently, however that fish has been in for about 4 weeks
What do you feed your fish? Aquarian
Any unusual findings on the fish such as "grains of salt",
bloody streaks, frayed fins or fungus? Slightly frayed dorsal and tail fin
Any unusual behavior like staying
at the bottom, not eating, ect..? as described above. Seems to be full of air

1. Your tank is ~30gallons and is WAY over stocked with 6 fish. Generally, goldfish need at least 10gallons each.
2. This means that you're probably going to have to change more than once a week.
3. You need to purchase a MASTER TEST KIT or have your water tested by your local petstore. If you decide to do the latter, obtain ACTUAL NUMBERS and not just "good" or "bad."
4. The fin fraying is most likely to water quality problems.

So to address the floating:
This is caused by a problem in the fish's swim bladder. This can be a symptom of various things. However with no other unusual behavior and judging from your description you've been able to give us, I'd say it's most likely due to water quality.

What to do:
Get your water tested and give your fish the appropriate volume needed for health. Also, reduce feedings to once a day and be sure to presoak food.

Thanks a million. =) I didn't relaise it was over-stocked as the guy at the petshop said it was big enough =/ Thanks for yourr help and I'll be doing as you suggest. One thing though. How long will it take for the fish to right itself again?

It depends on the severity of the situation. When swim bladder problems are caused by acute waste exposure, you'll probably be okay in a month or so in good prestine water. However, you must get the levels checked and fixed ASAP, or there's a potential that something like this can be permanent.

How are things going?