the tropical tank is easy, save as much water as you can,take out the decor plants etc, put the fish, heater (turn off the heater at least 10 minutes before you take it out of the water) and filter in a bucket (use the one you have for water changes) clean the gravel from your small tank and put it in your large one, add more if needed (making sure you wash it as well), arrange any decor, add the water you have kept, top up with warm water add dechlorinator, add the decor filter and heater, bag the fish and put them in the tank as you would if you had just bought them, make sure the temperature is the same and release them as normal.
the coldwater tank is much the same obviously without the heater.
if you have bought all new equipment for the tanks you could set up the new ones before dismantling the old ones and run the new filters in the old tanks to let them start cycling before you transfer them to the new tanks, i would also transfer the old filters to the new tanks for a couple of weeks to ease any problems which may occur.
have fun, algae eaters are quite difficult to catch I seem to remember!!!