Switching Tanks

Question
I currently have a 10 gallon tank. I purchased a 20 gallon tank that was used for some other animal. It has wood shavings in the bottom of it. I cleaned it out how the local pet store told me to do so and now I am wondering. What tank will be better in the long run? I already have everything I need for the 20 gallon except for the appropriate filter since the 20 gallon has the shape of a ten gallon but its more tall than it is wide. Also, what should I check for before using the 20 gallon tank? I am afraid that the joints in the tank won't be able to support the amount of water it will use. Please help. Also I currently have 3 swordtails..1 male, 2 females, 2 black tetras, 1 unknown tetra, and a Platy in my ten gallon. When I set up the 20 gallon, what should I do with the ten gallon?

Answer
Hi Lisa:  In the long run the 20 gallon tank will be better for you.  You will need to get the appropriate filter though.  To check if the tank will hold... fill it with water and let it sit for about a week. If it doesn't leak then it is good to go.  Keep the ten gallon tank as either a breeding tank or a hospital tank.  You will eventually need one or the other... we all do... hope this helps.... dave