Besides, if you have your hand on the end going into the bucket, you can quickly stop the flow of the siphon is one of your fish gets into the vac when it's not suposed to. If they get sucked into your vac's tubing, let them run into your bucket (you ARE using a clean bucket, right?) and then net/siphon them back into the main tank. A little stressful but they'll probably get over it quickly...kinda like a flume ride at Wet'N'Wild.