I think you will be ok with the 5 x 3 x 2. Motoros can and do get big, but not all reach 24". If you are keeping 2 rays and no more, they'll be ok for awhile. Obviously bigger is always better, but not everyone has room for an 8 x 4 x 2. If you start with small rays, the 5 x 3 x 2 should be fine for quite awhile. You can always build a bigger pond or trade them for smaller rays if they get too big. We've got several mature males all under 16" that are several years old. Females seem to get bigger faster, as most of ours are 18to 20". I love big tanks (we use 8 x 4 x 2), but I would not have a problem putting a pair of these rays into a 5 x 3 x 2. Just my 2 cents.
Pat
Amazon Stingrays
