I know what you mean allan about finding that sweet spot, i think what helped me was the fact that i got rid of that rock pile i had and opened up the tank more, to say, as for moving the pwrheads i really only added one. which i guess, worked, all in all. it was mainly luck for me. My tank has really come a long way since. that and it could have been new tank issues as well that finally worked themselves out. keep us posted.