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Do a water change before you leave to make sure the fish stay healthy while you are gone. If you have an overcrowded tank it is a must to do a water change before you leave.
Make sure all area's (Especially the open area in the back of the tank) are covered and do not leave the lid open. There is usually a plastic cover that comes with the tank hood that you can cut to fit the open area in the back. It is no fun to come back and have dead fish on the floor.
Get a timer for the light so there will be no changes while you are gone. I keep a timer on the light full time so my tank always gets the same amount of light. If you have a live plant this is important for the health of the plant.
Make sure everything is working and will continue to work while you are away from the house. Be sure to check for new products for travelling at your aquarium store. There are always new gadgets out there that you can get.
Something that I have learned is that the aquarium takes care of itself for the most part. My aquarium is about 90% automated and requires very little work. The light is on a timer so the only regular task I have is to feed the fish. The other task I have is a monthly water change.
Unless you are planning an extended vacation over 4 or 5 weeks your aquarium will not have many problems. The only loss during the vacation will be the fact that you can't check to see if the heat and filters are right. To solve that problem just ask a friend or neighbor to check on it every once in awhile to see if everything is alright. These tips should allow you to take worry free trips and to keep a healthy aquarium to come back to.