Good looking green terror. Large cichlids are pretty intelligent, and I find they can be "moody" and even throw tantrums or react negatively to changes. The arowana and leaving the tank probably makes the GT feel less comfortable, as the larger fish moving around would distract attention of predators (you, in this case) from the GT. Floating plants are something that I recommend a lot when fish are people-shy, as the fish don't feel so exposed. It also hasn't been that long, I might just give him some time to adjust to the changes, and try to keep hands out of the tank as much as possible.
