aaahhhh, not sure but would this effect the levels:
i have the overflow pipe right down into the sponge chamber and its nestled in some fine filter floss ( to keep splashing down )which every now and again keeps moving to one side, heres what im thinking is it possible that when the floss is directly under the pipe its holding back some of the water in the pipe and then when it moves to one side its letting the water run out.....umm dont know!!! what do you guys think, thanks for everyones help and patience so far.