i bought a gold nugget pleco about 2 weeks ago, put him in an established 10 gallon tank, he ate all the algea off the walls, ate the algae waffers that i put into the tank and was doing fine. i woke up one day and he was stiff as a board. i have heard they were a tuff fish to keep but i thought he was doing fine. any suggestions on what i did wrong ? my parameters are completely normal.

do you salt your tank? salt tends to kill plecos also what do you keep your water temp at?

Read the second ''post'' down from the ''wife and husband'', and also the 5th post down.
http://www.aquahobby.com/gallery/e_nugget.php

Also they can get to be up to 8", small for a pleco but still quite large for a 10 gal. If you are considering getting another, be ready to give him some more room later, and some driftwood to gnaw on. Most plecos love driftwood. It seems this species even relies on it to some degree.

Even if your params are normal now, these particular plecos are seemingly very sensitive to any fluctuations.

Edit: You may wish to find out from wherever you purchased your Pleco from what your suppliers tanks PH are at, if you haven't already. I've lost some shrimp because as I found out later the stores PH was a bit alkaline and mine is fairly acidic.