a 20T is really on the hairy edge of being too small.
SH represent a huge bioload on a system, and you'll be hard-pressed to keep up with water quality.
also, as mentioned, 74*F is about as high a temp as you should keep tropical
SH. the reason being that
SH are extremely susceptible to bacterial infections, and the bacterial count in a warm tank is quite high, a good deal higher than a cooler tank. we see LOTS of
SH getting sick when the summer temps raise peeps' tank temps.
another issue with plumbing the two systems together is that the
SH tank is going to pull the water quality in your reef down.
when it comes time to get your
SH, i can't stress the recommendation of getting TRUE CB
SH from a reputable breeder or hobbyist breeder. most of the
SH you see in the
LFS are raised in net pens in the ocean, and are subject to the same pathogens as WC's and should be prophylactically treated accordingly. i should add that these
SH are usually touted as being TR specimens. these fish have been raised for traditional Chinese medicine, and were never really meant to be sold as aquarium stock, altho they do make it into the trade. most folks have had dismal results with them. they are typically H. kuda, altho there have been some questionable H. kelloggi and some H. reidi as well. also, there have been a lot of cases where these
SH may or may not take frozen mysis, or stop eating it. true CB's are disease free and will come to you happily eating frozen mysis.
sorry for the long post, but that's the skinny...