imbalanced goldfish

Question
Your mailbox was full, so I went ahead and changed 25% of the water, and added a teaspoon of Fungus Eliminator by Jungle Laboratories to the ten gallon tank the 2 fish live in.  The tank has been established for about 16 monhts.  Toshi is aprox. 2 1/2 inches long, total length.

I examined Toshi more closely, and noticed that he has red streaks in the center of his tail near the tip, nto close to his body (bacterial infection?).  The tips of his tail are  pale, and this morning one tail tip is frayed, very white.  

The first day he was acting off he was just swimming oddly, there were no red streaks.  Day 2 red streaks and pale tail tips.  Day 3 swimming better, one tail tip very white and  frayed. From my research I think its like finrot.

He is a brownish gray, maybe a pom pom, his nostrils are slightly pronounced. He is swimmng more normally now, but he is hiding in his "cave" so I know he is not well. He is eating, and none of the other symptoms you describe are apparent.

His water definately needed changing.  We added some live plants a few months ago, could this have altered anything?  I also changed from one brand of flakes to another a few monts ago.  

I bought a new filter, but removed it after reading the directions on the Fungus Eliminator. How often do I add it (if you think I should).  I do not have a water testing kit.

The tank stays at 72 degrees, I have not added the heater I bought.  Today I think I should put it in.

There are a few tiny snails in the tank (from the plants).  The majority of plants are fake.  The other fish is a vailtail, they have always been together in this tank, no other fish.

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Followup To
Question -
My goldfish Toshi is swimming in a vertical position, looking ill.  This morning he was at teh bottom of the tank.  He did swim up to eat, but it's obvious he is not well.  There is one other fish in the tank.  I have had the tank with just these two fish for over a year.  

Is there any treatment for him or is it too late?  I have plastic plants in there, gravel and one live plant.  Nothing has changed in months and months.

Help!  Thank you,
Robin
Answer -
Hi Robin;

Make a 25% water change right away and give me more info about your fish and their tank;

Does the sick fish have any abnormal color changes, puffiness, blotches or spots on him anywhere?
Do his eyes look like the are protruding at all?
Do his scales look like they are sticking out?
How many gallons does the tank hold?
How big are the fish? (in inches or cm)
Does it have a filter?
How often are water changes made?
How much water is changed at a time?

Let me know as soon as you can....

At Your Service;
Chris Robbins

Answer
Hi Robin;

I think it is a bacterial infection, you are probably right about that. Fungus Eliminator works for that too. For a 10 gallon tank you need two teaspoons of it. Do a 25% water change first. Four days after the first dose, make another 25% water change and add two more teaspoons of Fungus Eliminator.

The plants nor the snails were the cause. It was simply dirty water. Goldfish are very messy fellas and must have a 25% water change once a week.

Goldfish do not need a heater so don't use it. They like their water in the upper 60's and low 70's.

I hope Toshi feels better soon.....

At Your Service;
Chris Robbins