As long as the automatic vacation feeder releases the correct portion sizes of food, it won't cause water quality issues in your betta tank. But malfunctions in rotating barrel feeders are not uncommon. If the feeding window opening is too large, the feeder can dump too much food into the water. In a short time period, the uneaten food starts rotting. The rotten fish food can cause ammonia spikes and poor water conditions. This is a major problem if you are not home for several days. Always test your vacation feeder before you go on vacation. Testing lets you make adjustments to the individual food portions and ensures the feeder works as it should.