Looks like a nice tank to me.
As for the ‘unknown’, my guess would be an A.stuartgranti “Chitamba Bay”, “Chilumba” or “Cobwe”.
Maybe this helps.
The Chitamba Bay has just a little yellow in his ventral fins.
The Cobwes’ ventral fins are slightly reddish.
And Chilumba has some yellow stripes in his caudal fin and little dots on his anal fin.
The rest of the body, from all three of them, is bleu with some faint, dark vertical bars.
Jimmy