Sick Fish

[fastpitch]

I am new to this forum. I have a sick (seems to be dying) fish. I do not know what kind of fish it is...but it is the same as the large blue and yellow fish at the header of this website. This fish is not able to swim upright. I have attached the best picture I can get of the large redish area on its side. Is there anything that can be done?

 

[Embrace]

First things first.

What size is your tank?
Have you cycled it?
What are your water parameters (not just 'fine', the actuall numbers).
What other fish are in there.

This will help us to help you.
Thanks,
Elise

 

[fastpitch]

1. My tank is 20 gallons.
2. It has been established for 2.5 years.
3. I do not know the actual numbers...only have test strips. Please suggest what product I should get to get these numbers.
4. I am extremely inexperienced...other fish: Another of the same one in the picture, angel fish, two dwarf catfish type, two grey tetra types (one with the flowy fins) and one orange one, two small fish with mostly translucent bodies, red heads and black and white tails, two zebra somethings (one bright yellow and one bright red)and one guppy.
   
   I have had very little issues with my tank. The fish all leave each other alone. The fish I posted the picture of died last night. I am now concerned about what may have gone wrong and will anything be happening to the rest of the fish. I will get whatever I need to get to test the "numbers" once someone can let me know what to do there.
   
   Last week I have tried to add two new dwarf blue gouramis. They both died. One appeared normal upon death and the other's fins appeared to be rotting away. I treated the tank with fungus clear. I didn't really know what I was doing...left it in for one day...was conerend about the fish then did a water change. Then two days later, I added the fungus clear back in for two full days, then did a water change...then the fish I started this thread about started swimming funny and I noticed the red marking on its side.
   
   Sorry for the book. I appreciate any help anyone can give.