Hello,Yes they do need big tanks.The bluespot(T Lymma)is a difficult one to keep in a closed system,but the(Dasyatis Kuhlii)witch is also called a bluespot ray dose well in the home aquarium,but is harder to find.Also along with the Triggers i would not put them in with Puffers,Butterflys,or Angelfish,They will nip at the rays fins and skin and eyes.