I haven't done an ecosystem on such a large scale, but I do have experience with the topic and what I have learned is that it takes time (duh). I know you hear that from everyone, but what I mean is this: I set up my ecosystem in a 7 gallon shallow. I put live daphnia and scuds into the tank after letting it cycle, and I just let them populate in there for a month. After that, I added blue dream shrimp and 2 stiphodon gobies, and let the shrimp populate for a month. After that, I added 1 hillstream loach, two galaxy rasboras, and two scarlet badis. I dont feed this tank, the rasboras and badis survive off the scuds, daphnia, and shrimplets. The gobies and loach survive off decaying plants and algea. The tank is heavily planted with hornwart, which gives the smaller creatures places to live and breed. Hope some info can be gleamed from this.
