“Scampering” over the sand and rocks like colorful aquatic mice, disappearing into caves and then popping out to look around, Blennies are quite captivating. Most are only 2-3 inches in length, but make up for their size with (usually) bright colors and (always) amusing antics. Blennies are generally hardy, but bear in mind that they are territorial and do best when provided with lots of rockwork and an ample supply of growing marine algae upon which to snack.