Wow! This thread has taken a turn. . .
Carpenter, I owe you an apology. When I told you to not tell people to learn to read, I assumed you had used it in your post. Now I see that you were quoting Ajones. I'm sorry. I hate it when quotes don't show up in a blue square; it makes me all confused.
Adastra- A "troll"? Ouch! Is name-calling really necessary?
Could we all please get back on topic?
So Ajones, I am confused. Are you going to be caring for the fish or is your aunt? I'm assuming that your aunt has very little or no fishkeeping experience. I thought that Blue Rams were pretty difficult fish to care for. They need very specific water conditions. Maybe German Blues are different (I have no idea, I don't know much about cichlids), but you should seriously consider the water conditions needed for the fish.
Danios are great. Really easy to care for and very active in an aquarium. Are you still thinking about making it a sorority of female bettas? If so, some research will need to be done since females can be aggressive toward each other or tankmates. As for the livebearers, I highly doubt they can change genders. More likely they were sexed incorrectly to begin with. I don't know how you tell the difference between male and female livebearers. Guppies are easily sexed, but I'm not sure about mollies or platies. (Sorry that I'm kinda clueless at this, I'm new to fishkeeping.)
Going back to the original question, danios would work great for a fish in cycle. But I think most of us on the forum would recommend using a fishless cycle. The shrimp method Adastra suggested sounds perfect for your situation.
Anyway, I think the most important thing for you to tell us now is who is going to be caring for the fish, have you picked fish yet, and what is your aunt looking for in an aquarium?
It's been 5 years...I'm no longer a newbie
20 gal long-otos, glowlight tetra, black phantom tetra, African dwarf frogs
56 gal-zebra loaches, serpae tetra, rosy barbs, bristlenose pleco
2 gal-empty (formerly Mercury-purple veil tail betta