wow, didn't know they get that big. He is in a 125 with peacocks and Haps a Frontosa and Calvus, is he OK to be in with them or will he think of them as food when he gets that big? He eats like a pig, might not be too long before he gets pretty good size, he's about 4.5"s now.
Yes, he will be fine in that tank long term with those inhabitants.
What concerns me is the Frontosa. It might not be okay long term with many of your stock list... Frontosa can easily eat some full grown Aulonocara species and some (but not most) Haplochromine species. I'd ditch it as soon as possible. They do better in colonies of their own than with other types of fish anyway.
16" would be an extreme case of a well fed male in a really large tank.
The Fossochromis is fine with the other fish. They are not much of a predator, other than opportunistic. Obviously a 8" or 10" could swallow small fish if they had the chance, but you could say the same about any fish that size.