turn your stereo up and the noise will go away
nah seriously, if the noise wasn't there before you fiddled with the system, then you have done something to it. it may not affect it at all, so don't worry too much.
if it were me, i would open up the tank again and repeat whatever you did the first time but TAKE EXTRA CARE to put it all back exactly as it looks like it should go. if the noise is STILL there..... use the "stereo interference" method