My fish keep dying

Question
I have a 20 gallon tank with guppies and glowfish and neons in it and they keep dying, my scavenager died and his eyes looked like they were sealed shut and I have lost 12 other fish today alone and Im not sure what is going on with my tank.  I have never lost this many fish before. what should I do?

Answer
Hi Beth;

You didn't give me much to go on I'm afraid. Make a 25% water change right away and hopefully they will feel better until we can figure this out.

I need to know more about the tank as well as your feeding and maintenance schedule. Here's what I need;

Can you see any other visible signs of disease on the dead fish?
How long has your tank been set up?
How big is your tank?
How many fish do you have?
How big are they?
What type of filter?
What is the water temperature?
Does the tank have a heater?
What are the pH, ammonia, nitrite levels?
How often do you change water?
How many gallons of water are replaced every time?
When was the last water change?
Do you use a water conditioner? What kind?
What kind of food do you feed?
How often do you feed the fish?
How many minutes does it take for the fish to consume all the food from all areas of the aquarium after you feed them?

Let me know as soon as you can...

At Your Service;
Chris Robbins