Black slug in tank ??

[jarrid]

I was looking at my tank w a flashlight last night when i noticed a medium snail sized all black "slug" with two medium length feelers coming from his mouth area. He had no hard shell, thats why i call him a "slug". If anyone could help identify this guy that would b great, i tried taking a pic but it didnt turn out so well. He was no more than an inch in length.