Further warning - Important: This only works for players who purchased the original Treasure Terrace which held 2 dragons and 10/gold. The new habitats currently available for purchase also hold 2 dragons, but only hold 5 gold/day. I've seen many theories on how to get "all the gold" and it seemed confusing, so I wanted to be sure before I put 2 dragons in one habitat that it was indeed possible to get 10 gold/day from 2 epic gold-producing dragons.
After sending a PM, I was told by a moderator who looked into this for me when Rose Gold was released, that no matter what I did, I could only get 5 gold per day from these new habitats even if I put two dragons in there. Apparently, this is the way TL has the habitats now. Sorry to say, but there's no special way of collecting to get 5 gold from each dragon in a single habitat, I checked. So, I had to buy a second habitat for my second gold-producing dragon. Eight Million coins for each habitat!! Just to get 10 gold a day.
The Treasure Terrace needs to be changed back to 10 per day with 2 dragons, or if they want to keep the habitats at a max of 5 gold/day for us newer players, they should give us more habitats (limit being one habitat for each dragon). IMO, I'm opposed to the latter choice, because I'm running out of room for habitats. I also don't see how this would work out considering many players already have 2 dragons in each habitat (which makes sense because they hold two, and the habitats are super expensive!) It's better, and fairer to change the habitats back to holding 10 gold/day.
Once new players understand that two dragons in one habitat still equals 5 gold every 24 hrs, they will know it's not worth the money to buy all the gold producing dragons. As it is, with a max of 5 treasure terraces, I will only ever own 5 gold producing dragons. Totally unfair, as I would like to have them all one day, but not if I can only get 5 gold with 2 epic dragons in one habitat. That's ridiculous.