for ammonia, water changes is the only way to remove ammonia and nitrate. the ammonia does remove by itself through water cycling unless there's too much in the water. meal worms are a good source. If you're going to be gone for a few days just put a bunch of guppy feeders in the tank. They will eat the guppies when there's nothing left to eat. I usually put about 2 hundred feeders in my 10 gallon tank when going on vacation.