They are quite aggressive. I would not suggest trying it to anyone that did not have adequate P keeping experience. They do not school like pygos. You have to have a constant eye on them, and alot of time to make sure things are going okay. I started with 10, but lost one after 6 months when I got drunk and decided to add my cf to the school. A few days later one of my golds was dead. Up until that point I had no major problems. Just so nasty tail maulings. Had to use a hospital tank probly 5-6 times since I got them in jan.
I think that spilos are a very good school, that requires alot of tlc. If you have anymore Q's just ask.
I would go with a shoal of all terns or caribe. I haven't seen anybody with a shoal of terns. That would be interesting. I love the caribe for there ferocity. Its up to you. I haven't had any experience with spilos so I couldn't say.
My advise to you is take a look at some pics and go from there. Find a fish that is interesting to you, for more then aggression. That way when you fish turn out to not be aggressive, you are not disappointed.
well said insinuasian.
i would go with a shoal of pygos and go for wild caught if your after a better chance for them to be aggressive so cariba or piraya or even wild reds or yellow natts (terns) depending on price restraints
i'm still waiting for some one to amaze me with a sweet geryii shoal. I would go with the geryii mainly based on its hyper aggression (so I've heard) and super cool appearance. if you put 6-7 8" geryii in that 180 with some kind of amazonian river theme, it would not only be awesome, but also pretty unique.