There is no room for pangasius sp. catfish in home aquaria in general, let alone your tang tank
. True monster fish, the smallest of the 3 most popular species will reach a min of 4' though they average somewhere between 4 and 5'.
A bristlneose would do quite well, no problems with that guy. They're great at taking care of unwanted algae and very hardy.
A bulldog plec may be a whole other story. Depends on adult size and species. If it's any type of rubbernose (Chaetostoma sp.) plec it would really do better in subtropical conditions with plenty of water flow. If it's a Parotocinclus jumbo it may end up being eaten. There's one or two others it may be, look around on
www.planetcatfish.com for exact species. If it gets bigger than 6" I'd find it a new home. Plecs are also territorial o you have to consider space and territory for each so that one doesn't get assed out if there's nore than one.
The zig zag eels should also go. Depending on pecies it will average 3' and possibly larger. They will eat any fish they can fit into their mouths.