Expert: Christy - 9/7/2008

Question
I have recently bought a 10 gallon tank and have 5 goldfish in there. when we first purchased it we bought 6 of the cheap goldfish they all died but 1 of them, we went and bought 4 different goldfish a little bigger than the cheap ones i am not sure what kind these are i am guessing common goldfish,my question is the goldfish that lasted has been sitting under one of the decorations and he has came out and swam around but it doesn't seem as if he is eating and that is what is worrying me, the bigger fish seem to push him out of the way and eat all the food, is there anything i can do about this, i am afraid it is going to die as well. we did find out why the others died, was because we did not know that the water had to be filtered for a couple of days before you put the fish in, i guess it is a miracle that the one did make it?

thanks for your help

Answer
Hi Anne
Sorry to say, but I think you're getting some poor information.
Technically, you don't need to filter or run a tank for a few days before adding fish to it.  You could set up a tank, add the water, and immediately add the fish to it.  Letting a tank run a few days with water is doing absolutely nothing to "prepare" it for fish.  That's a common misconception given out, I know I've seen it on new aquarium instructions and pet stores are notorious for dishing out that kind of info.
One thing that is good to do, is what's called a fishless cycle.  Here's a link that explains what the nitrogen cycle is:

http://freshaquarium.about.com/cs/biologicalcycle/a/nitrogencycle.htm

All new tanks go through this process.  Now for fishless cycling, basically what you do is set up the tank, and put an ammonia source in the tank to start the cycle process.  Most commonly and easiest to use is a frozen cocktail shrimp.  Some will use pure ammonia(which is too hard to find now a days), or fish food.  You don't anything to the tank, just let the ammonia source rot and that will start the beneficial bacteria growing.  I would also suggest picking up a good test kit, I like API's Freshwater Master Test Kit.  Has all the test's you need in it.  

Now, you've already gotten fish in the tank, so it's too late to do the fishless cycle.  So you'll have to do a bit more work to keep the fish alive.  Unfortunately, goldfish are uncompatible with a 10 gallon tank.  Depending on the types of goldies you have, they have the potential to grow between 8-12+ inches, with the common and comet varieties over 12 inches.  It's recommended to have at least 15 gallons for one goldfish, and that's just to start out.  Obviously a 12 inch goldfish needs larger then that.  Fancy varieties can do well in about 20 gallons for one.  So, with 5 goldies, you really should have at least a 55 gallon tank-and that's probably pushing it.  Anything less, and you will constantly have problems with water quality in the tank, it'll just be impossible to get it right.  So, I would strongly suggest returning all the fish, or upgrading to a much larger tank, or return a few of the fish and get a larger tank to accomodate the ones you keep.  Sorry, but I just see no other option if you want the fish to survive.  
The one that isn't eating, is most likely suffering from ammonia poisoning, and the bullying by the other fish is very stressful to fish.  

For the types of goldfish you have, common and comets are usually the ones sold as "feeders".  They're also the ones that grow larger.  Here's a site with the different types of goldfish, also search around for more info on goldies there:

http://www.kokosgoldfish.com/ftypes.html

Good luck and let me know if you have more questions.

Christy