is my fantail goldy dying

Question
I have a 20 gallon tank and 2 goldfish. i have had it for about 4 months.
within the last day, one of my fish has been acting like he's dying- he floats
vertical head up on the top of the water, sucking in air. then he sinks down to
the bottom without using his fins and sits there on the gravel unless i tap on
the glass. i have put two packets of "maracyn-two" antibiotics, but he doesnt
seem to be doing any better. i feed them flake food, and i recently added a
live plant. he has no external signs of infection, no discolouring, nothing
looks wrong.i just know he's not all right.  what is wrong and what can i do?!
im afraid i will wake up in the morning and he will be dead!

Answer
Hi Shannen
How much and how often do you feed them, do you soak the flakes beforehand, do you have a filter in the tank (for two goldfish, you need good filtration - I recommend and under gravel filter combined with a bio-wheel), and how often are you changing out their water? Lastly, what temperature do you keep their tank at, and do you ever test their water quality? This information is important in helping me help you figure out what the true issue is. Most often laying on the bottom of the tank means the water quality is poor, and you need to start changing out the water more often. Your fish may be exhausted or suffocating. This is not always the case though. But it's not really a good idea to medicate your fish without first diagnosing their illness. In most cases, you want to save medicine as a last resort, as it's much healthier and safer for the fish to recover naturally with the help of some water changes. Please either respond with the above information provided, or feel free to look up Goldfish Care web sites for more information so you can find out why these things are important (Please check more than one site, and only ones that are not by just one person, and you should always double check the information)! Best of luck to you.