Oooh heck Brad, you've got some fish in there that wont fit in a couple of months. Silver sharks and common plecs are going to need a muuuuch bigger tank - I'd take them back and swap them for something more suitable.
Silver sharks get to 12" and need to be in groups of 5 or more - to have that many you'd need a 6 x 2 x 2ft tank. One common plec needs a 4ft x 18" x 18" tank just in order to move around (they get to 12-18"), and in order for two to make territories and have enough room, you'd be looking at the 6ft tank again. Dunno what the spotted catfish is, if it's a gibby - they get even bigger
Frozen bloodworm is fine - just thaw it in a cup or chuck it in frozen - depends on how your fish like it
I was told about the size of the plecs and sharks not long after i got them but i'v had em for about 6 months now and the plec's have grown about 3 inches and the sharks half an inch so im hoping i have found myself a few genetically small fish