id say the foaming types. we have anti-bacterial foaming soap at my house, always liked it cuz it washes away really easy, not sure about the residue though, just rinse thoroughly. never had a soap problem in my tank before.Brent;2913790; said:i wash my hands everytime and i use dawn to wash because i always figure dish soap washes off completely and wont get in the tank any soaps anyone recomends for the fish's sake to keep from getting left over soap residue in to the water?