Size difference between tubifex and blackworms

[stanleyc]

Is there a difference in size between the 2 worms? What are the nutritional differences?

 

[Jennewt]

Tubifex are generally up to about 1 inch long and pink/orange in color. Blackworms are up to about 2 inches long and reddish-black in color.

Nutritional values are very similar. Both are included in this nutritional analysis of feeder invertebrates (PDF):
http://www.nagonline.net/Technical Papers/NAGFS00397Insects-JONIFEB24,2002MODIFIED.pdf

 

[knifegill]

I have collected tubifex worms in excess of 4" here in the cold Northwestern USA. But, yes, blackworms typically do range 1" to 2" to sometimes 3" at their absolute grandpa hugest.