I have the Penn Plax also and have had no problems.I lay a 2x2 across the top of the tank and fasten the feeder to it.This prevented moisture problems.They recommend using pellet food.That will help with moisture problems also.The one I have will feed the amount you set, twice in a 24 hour period.Its battery operated.I have been away 1 week and it worked fine.Paid $8.00 for it.