After owning my first Synspilum for 3 months now (see below), I've noticed/observed the following in regards to the species.
1. They grow insanely fast! Mine has gone from 6" over 10" in this time. In addition, he's pushing 1.5" thick. Mine goes nuts for sinking carnivore pellets, and is not at all fussy about foods. He will eat anything I put in the tank.
2. They don't behave like a typical wet pet (i.e. Midas, RD, Oscar, Dovii, etc.). They're a bit more cautious, and seem to startle a bit quicker than some of the more interactive species. However, they certainly don't hide all day either. Mine paces the front of the tank when he's hungry, and doesn't mind me being close to the aquarium. On a scale of 1-10 for interactivity (10 being the highest), I'd put them at a 6.
3. They show amazing colors! I'm most amazed when the sun hits the fish just right in the afternoon. Mine shows blues, reds, pinks, yellows, greens, etc. They're spectacular to look at!
4. Mine is not at all aggressive (aside from when he wants to spawn with the Fenestratus). He is a gentle giant who swims around looking for anything he can eat. In fact, my small 3" Convict pair chase him away with relative ease when he's too close to their territory.
5. All in all, they're a great species to keep and I really enjoy mine.