Not typically, no. It can be done, but you would be likely to have trouble (I know, I know - some of you have done it for years, but I think it's risky and I have seen too many examples of it not working). Tincs are easiest in 1.1, just like most dart frogs. I have had good luck keeping Auratus and Terribilis in groups. I do have some aggression in the Terribs, but it doesn't result in enough impact that anybody loses weight or stops breeding. There might be aggression with Auratus, as well, but I wouldn't know it because I don't see them often enough. I had good luck with Anthonyii and continue to have luck with Quinquevittatus (though see my note on Auratus above and that applies to Quinqs, too). Galacts seemed ok when I had them, too. All of these are just suggestions, though. Any of these suggestions might results in aggression that can be very dangerous to the frogs.
Unfortunately not really. A lot of the species we have in the hobby are territorial so there is often same sex aggression (although which sex is more aggressive depends on the species). Tincs aren't group frogs and its goes badly the vast majority of the time typically the same with pums. I tried two female tincs in a heavily planted 55 gallon viv and the dominant frog went after the other within about 5 minutes of being in the tank. Leucs, auratus, galacs, phyllobates, are a few of the larger and group tolerant species.
None. That's a rubbish size for frogs that are that big. Not the answer you're looking for, but anything that's "x" x 12 x 12 is really not ideal for darts. Also, try not to hijack someone else's thread You can start your own for unique questions, or try to utilize the search feature which will pull up all kinds of helpful threads and knowledge.
Why does no one say ameerega? In the years i've been in the hobby, I've seen almost every morph of this species kept in group and always succesfull. Even after many years they remain to trive well in group. This is not always the case for other genus.
My A. Hahneli are also kept in group of 4 since 2014 . Currently I keep their 1 year old offspring are in a group of 14 animals together and I've seen none aggression or problems, all frogs are very healthy, same size, males calling next to each other, no dominance between females,... Only positive things to say...
Ameerega are great. I had a group of bassleri for a while; still keep a pair of females together. They're beautiful, and hands down my favorite genus. Just not a frog I'd generally recommend starting with as they need a ton of space, are harder to breed, and froglets can be a tad more delicate than other species.