Tiresias,
I have a bi-color blenny and he is sooo cool. They have tons of personality
Personally I would not put a blue hippo or yellow tank in a tank that small, they get pretty big.
http://marinedepotlive.com/ This site gives some good info on the size, feeding etc....
If you decide on the Tangs, this is information given to me by Naesco that I have saved when I get my 155gal tang tank ready. Hope this helps
"Go out and buy one but do not buy the first one you see. Make sure he is 100% healthy. No marks, tears, spots; clear eyes Make 100% sure he is fat no thinness along the bottom: fat!
It will soon be obvious to you the fish that you will buy. He will be alert, interested in you ,and you will immediately feel attached to him. Remember healthy first than attachment.
Ask the LFS to feed him. He should dart out and really go for the food.
That is the only fish you want to buy. He should be small between 1.5-2.5 inches no more.
It may take you a month to find him or you may just luck out.
When you carefully put him in your tank keep the lights closed for at least one day and don't bug him. Let him adjust to your tank and its inhabitants. He will soon be out swimming around. Feed him nori and dried shrimp soaked in garlic extract and selcon for the first 10 days. This is to beat any ich that he might have. Than you are home free. If ich surfaces again start the garlic treatment ASAP.
I am a recommending you do this because I assume your tank in in good shape.I move new fish through my small reef to my big tank. The stress of a brand new 180 for a brand new fish is lessened when you keep him in the small tank for a while."