Mine are not interested in algae wafers either...just the algae. Their diets need to be supplemented with vegetables. zucchini is what I feed my ottos. I just slice a piece or 2 off and put it in the tank....they go crazy over it. You can also use cucumber.
let them have a reallly yuckky fixture from one of your other tanks to snack from.... it will be squeaky adn only need sterilizing. And the like blanched zucchini
and an occasional goodie like bloodworm.
"Fish! Thank You! Oh, tropical huh? Did you buy a heater? Auuugh!"
Mega-pet stores prolly should not be allowed to sell animals as retail "items".