Youve gotten 38 replies to your question and a lot of good advice. If none of this makes sense to you and you dont realize where you are headed with a dovii in a 75 gallon tank & tankmates, by all means, use the search function located on the left hand side of the forum towards the top (under where your private messages etc are.) Search for "dovii tankmates" "dovii tank size" "dovii" "killer dovii" "crazy dovii" and any other combo of words with dovii in it.
In reference to your question about keeping it with the africans you just got, no. The dovii will more than likely outgrow the africans in the next few months and then let them know where they stand shortly there after.
There is TONS of info on MFK relating to dovii (probably more than any other fish), all you have to do is search for it.
Good Luck.