New tank problems

Question
Hi Chris,
I'm brand new at this, and I need your help.  I just bought a 5 gallon hexagonal tank with a top mounted filtration system with a biowheel.  I set it up 2 days ago and added some water conditioner and chlorine remover and eased the plastic bag containing 3 goldfish (2 small fantails and 1 bigger common goldfish or Comet).  After 15 minutes, I released the fish into the tank.  I've fed them 2-3 times daily.  The water became foggy yesterday, but cleared up today.  Sadly, the small gold fantail died this afternoon. :(  His tail looked like it was bitten off by the other larger Comet or Common Goldfish (not sure what it is, but it's about 4 inches long) and he had a little red spot at the base of his tail.  Before he died, I noticed some white flaky areas around his gills and he seemed to stay up at the top of the water breathing all the air bubbles accumulating at the top of the tank.  He kept getting chased around by the other white fantail with the red colored head.  Now this white colored fantail keeps swimming up and down repeatedly for hours at the front of the tank while shaking.  He looks like he's gone crazy.  I'm guessing he's stressed.  I don't want him to swim himself to death.  I tried to add more of the water conditioner to reduce stress.  Today, I bought a bottle of "Cycle" concentrated bacteria and added 1 capfull to the tank to help reduce ammonia and nitrite levels by helping the creation of bacteria colonies on the filter and biowheel.  I thought that might help too.  The Comet seems healthiest of all, but gets a little jumpy sometimes and tries to snap at the little red headed white fantail that's left. I'm not sure if he's trying to kill him or if he's stressed too.  I think the tank might by too small for him, or maybe the decorative plants inside are inhibiting his need for free and wide motion.  These are my concerns.  If you can please help, I'd really appreciate it.  I don't want to lose another fish. Thank you.

Answer
Hi Basil;

Poor guys. Goldfish get too big for that size of a tank and it's also new. It's going through the break-in period. Toxins rise to lethal levels when too many fish are in there to get it started. Make a 75% water change right away and take the goldfish back to the fish store.  The water change will get the ammonia levels to a tolerable level temporarily. Get one tiny little half-inch fish and do not add any more for 6 weeks. This will be your break-in fish. Good ones for a little tank like yours would be a danio, white cloud, neon tetra, or a cory cat. Here is a link to my article on new tanks;

http://www.xanga.com/Expert_Fish_Help

Goldfish need at least a 10 gallon tank for just one. That big guy actually needs to be in a 20 gallon. Goldfish all get to be at least 6 or 8 inches long (not counting the tail) so he has even more growing to do. Here is more about goldfish and their needs;

http://www.firsttankguide.net/goldfish.php

I hope everything turns out okay.......

At Your Service;
Chris Robbins