Wippit Guud, I have a 90 gallon tank with six 6 to 8 inch piranhas and I do not have any problems cleaning their tank. It takes a little extra care but that is all. The worst thing you could do would be to hand feed them. Then they will associate your hand with food. I toss the food into the tank from a short distance away. All they think when they see my hand is net and they take off for the far end of the tank. They are very timid and not anything like the horrid monsters they are made out to be.