Shock From Water, Help.

[lifeofbrian]

I put my finger in the tank to free a trapped fish and got a small shock, I did (very stupidly) put my hand straight back in and didn't get a shock. Are my fish in danger, I read that they are safe from shock. The only thing I have in the water is a heater so I switched it off, I have a pump that is in the cabinet below, so if that's the problem then the water from that is obviously touching the water in the tank.  How do I find out what the problem is. Could an RCD plug find the problem?
 
The tank is a few years old and this is my first shock (apart from the dragonfly nymph that jumped out at me), I haven't disturbed the heater since I last had my hans in there. What should I do?

 

[lrhodes]

Ah! The only time I've gotten shocked from my tank was when my over head light falls in the water and I go to pull it out without unplugging it! (My son broke the hood, so it easily falls in.)
Hmmm... have you touched it since unplugging the heater?

 

[lifeofbrian]

No, after realising how stupid I was for putting my hand back in I haven't touched it.

 

Ah! The only time I've gotten shocked from my tank was when my over head light falls in the water and I go to pull it out without unplugging it! (My son broke the hood, so it easily falls in.)
Hmmm... have you touched it since unplugging the heater?

 

[Tartan-Guppy]

I would very much think the heater is the most likely cause. I'm not saying no, but I doubt the charge would have come through the pipes of your filter
 
Unplug it (with dry hands) then remove it from the tank
Check it thoroughly for cracks and also check there is no water inside (from micro cracks that you may not see)
 
I think the fish are less affected as they are not ground to earth, but not entirely sure on that. However I think they are still affected by it to some extent