Old fish tank

I know this is an amazingly bad photo, but I included it because you can kind of see how badly crowded my old fish tank was. It is about 13 gallons, and according to some websites (I think they're excessive) you should only have 1 fish per 5 gallons, which means I had 14.666 too many fish in the tank. Actually I think that number is a bit ridiculous for carp, so I'm figuring 1 gallon per fish will work. Less than that worked last winter, I had about 15 in this tank all winter and they did fine although they were smaller back then and they hadn't reproduced. Anyway, I bought a new fish tank on Craig's list yesterday, only 4 blocks away. It was advertised as a 20 gallon tank but I think it is bigger ... I haven't done the calculation for the real volume but I will. I washed the tank out and ran it over night to stablize it, and today I put 10 of the biggest fish in. I am planning to run two tanks all winter because I don't think either are big enough for the fish now. I'll post a picture of the new tank soon, not that it's so excitingly different from any other fish tank.