right about the water getting stagnant i was going to say that but i got beat to it. im not sure how you could cure this, but with 50gal. to refill you must have a source of water near by. and also the cameras are a real risk, heard about someone getting it that way, but they had a LOT more than 4 plants, the barrel will stick out more than your plants would. check into harvesting rain water/barrels they have mosquito cakes and things that should help with your stagnant water. infared goggles? $$$