These feeders are gel based instead of plaster based. They will not cloud your water.
Rivers to Reef says: If you are going to be away for a couple days or a long weekend, don't worry about your fish. Feed them right before you leave, then feed them right when you get home and they will be fine. For longer trips, remember it is better to underfeed than over feed. If you are going to be gone for 7 days, use a 5 day feeder. If you are going to be gone for 10 days, use half of a 14 day feeder. If you have a low fish population or a small tank don't use a whole block.
These feeders are not the best, if you want true piece of mind get an automated feeder and set it up a few days before you leave. Automated feeders feed the food your fish are used to and are more reliable than this gel block or your "friend that had that fish tank that one time".