I just noticed that you are not the OP, so we (several of us) have mixed up two threads from two individuals. It would be better to start your own if you want to develop it, I'll leave that to you. A moderator can copy over relevant posts if you do this. In the interim, I will answer your questions and post some additional ones.
My first question is, what are your source water parameters? Adjusting these, depending what they are and what you would like, is not easy nor inexpensive (depending). The GH and pH of your tap water is the starting point; if it is suited to angelfish, that avoids a lot of extra work and risk to the fish. Angelfish are soft water fish, but they have quite a range into the moderately hard area.
Second, it would seem you do not have the angelfish now; do you intend four (two "pairs"? This is almost guaranteed to fail, even in a 5-foot tank; in an 8-foot two spawning pairs might work out. Also, the angelfish have to select each other and bond; any female and male may but more often may not bond, and the female is not long for this world. There are some important issues with this species, and I've no idea of your level of knowledge so I don't want to presume either way, but can explain further if asked.
Tankmates for angelfish are a bit tricky, but doable. Linear small fish, like many of the tetras (neons and cardinals for example) and rasboras, are not advisable. The rounder disk-shaped tetras are usually OK, just make sure they are not a species prone to fin nip, nor an active swimmer. The Rosy Tetra (Hyphessobrycon rosaceaus) and similar species tend to work well. As do most bottom fish, but nocturnally over-active catfish are not advisable, such fish can seriously stress out sedate fish. There are others, I will wait until I know more of the intention re the angelfish.
Now, a word about googling information. Much of it, not sure I can say the majority but it certainly seems likely, is completely unreliable and best ignored. We have had more than a few threads lately dealing with this problem. You really have to know the source of the information in order to trust it. There is a lot involved in the life of a fish as it relates to its "environment," quite different and far more complex than any terrestrial animal. And environment involves water parameters, numbers of the species, space, other species, habitat features (some may be crucial to the species' life), etc. Research is key to success.
). I like the otocinclus, a pair of Gourami. And maybe 2 different types of dwarf cichlid pairs.
even with the respect du to the iconic absolute must Mad Max 
