how to transport an established tank to another city

I suggest buying a couple of cheap water coolers and placing the fisn in them. If you could purchase a battery operator pump, it would help in iarating the water providing the valuable O2 needed for the trip. That is not absolutely neccessary.
Use ammo-lock chip to prevent your fish frfom NH3 poisoning.

Empty your tank of water except for a a little it of water just covering the gravel. This will prevent the bacteria from dying during the trip. Take filter media and put them bag containing water again to prevent the bacterial colony from dying.

Rohn

I dont know if this will help, but maybe a small filter on the cooler to keep the bacteria alive.

Ok there is probably a few ways that you could do this. I would go the bucket method.First what you need to do is reduce feeding as much as possible from about a week in advance, then one day before you leave dont fed them at all, this will reduce wastes that the fish produce on the trip. Get a few snap lock buckets, put the fish in one or two of them and the filter media in the other one. fill the buckets with water from your tank, and I assume they sell ammonia lock in the states so get some so as to reduce ammonia for the trip(no filtration). This is the hard part you may have to buy a battery powered air pump if you dont have one. Then you put air stone's in the buckets by cutting air holes in the top of the buckets, this will also allow for the air hose to go in as well as breathing holes (put the air stone in all of the buckets , even the filter media bucket). As for warmth, if you are in a car the temperature should not drop to much but just to be sure wrap the buckets in blankets or some kind of insulation. You should be fine and remember when you get to your destination fill the tanks straight away , declorinate the water and slowly acclimatize the fish to their new water ,b/c it will probably be different to what you have now. If you can test the bucket water and the new water to see the difference.
Goodluck

my trip is only 1 hour...but I asked this same question on Weds...below is the link to the answers I got. There are plenty of good tips.

http://www.aquariacentral.com/forums/showthread.php?t=50638

3oo miles in 4 hours? dang.....I can go that in about 2 1/2 hours......... Anyway, if you have live plants, get a 5g bucket or two, depending on how many fish you have.....put your tank water in the bucks about 3/4 full, unless you get the lids to,,,then cut a nice center hole in the lid, fill up a little more, toss the plants in, then the fish, drain the tank, leave just enough water that i;s right at gravle level,,,,,,,if you run can filters, leave the water int hem and pack um standing up,,,,,,when you get your knew spot set up tank, dump the buckets in tank, fire up the filters when you get it all set up,,,,,should be no troubles in it......how I have always done it, but the filter part,, i just drained the water out of them inthe past......

you people should stop driving 100-120mph which is what you'd have to do to travel 300 miles in 2.5 or 3 hours. Your bound to hurt someone at those speeds.

160km/h Thats like super fast.