need help asap! my tank is shocking me

[marvinsae]

ok i noticed the past couple of days when i put my arm in i would get a tingly feeling, i just thought it was my nerves. today i got a HUGE shock and i dont know where its coming from. everything i bought new EXCEPT for my pump which has a nick in the wire and also 1 power head was purchased used. most likely the pump? however the pumps on the bottem and i dont get shocked when i touch the sump, but only in the display tank around the same area as the return hose. i dunno if that makes any sense and i definately dont wanna test it out again without hurting myself. what should i do. as of now i have everything turned it, the electric current aren't effecting the fish