The Central Tray, as it was originally know, has gone through many iterations since the original building opened in 1981. From bottlenose dolphins, to sea lions, and beluga whales before becoming the Wings in the Water exhibit and finally Blacktip Reef in 2013.
For 30 years, the tray remained the same - a bare concrete bottom, painted a light blue color. The 'pit' was temporarily covered for a time in 2008-9 after that section of the exhibit began to deteriorate. The exhibit was then lined with sand to disguise the 'pit' cover. While aesthetically pleasing, the weight of the sand ended up causing the collapse of the cover itself and was then removed.
Originally, the bump out window was obviously not present and the underwater viewing area was quite dark. The viewing windows were the same shape and size as the two windows flanking either side of the bump out window today. Above, the guest pathways were the same, minus the glass siding. On the exit side of Blacktip Reef, an entire guest walkway was cut back considerably to create the sandbar section of the exhibit. Also removed was a cylindrical tank which held numerous exhibits over the years.
Renovations to the tray were needed for years even before Blacktip Reef was even conceived. Originally, it was to be renovated and turned back into the same stingray exhibit, but soon evolved into what the Aquarium has today. There are some good pictures that folks have posted in the Zoo Chat photo gallery that can jog your memory and the Aquarium's YouTube channel still has videos posted of the Blacktip Reef transformation.