Foam/frothyness

Question
Hi, we have a small tank (just under 3 gallons) with two fancy goldfish. The tank has been set up for 2 months and runs on an under gravel filter with air rock.  It started last week producing a small amount of froth on the surface of the water around the edge of the tank only.  The fish appear to be perfectly healthy still, but I am worried this froth may be harmful to them.  Any suggestions as to what it may be or how to stop this happening?  Thanks.

Answer
Hi Liz;

The foam is actually due to ammonia buildup from their waste. Goldfish are tremendously messy fish that need lots of room and good filtration to survive. Your guys need a bigger tank of at least 10 gallons and a different type of filter. They are growing so it will slowly get worse for them in there. Change 25% of their water every two days to keep the ammonia lower until you can get them into a bigger home.

When you shop for a bigger tank, hopefully it will be a ten gallon or larger. Get the type of filter that creates a kind of waterfall and hangs on the back. It's called a "power filter". With the tremendous amount of waste that goldfish make, an undergravel is just not suitable for them. Undergravels are suited for smaller community fish that stay very small (a couple of inches) and have slimmer bodies. Goldfish get to be 8 inches long and are deep-bodied. Power filters are made to remove larger wastes of fish like yours. Here is a great web page with info about goldfish and their needs;

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

At Your Service;
Chris Robbins