Hi fish keeper !
Lovey fishes you have there mate ! Nice !
So 190 gals is a 5 foot tank , you have a 6 foot tank, cool !
First of all you have to decide what you want mate. You need to decide if you want to keep fishes for the fishes wellbeing or for you to just have a nice 6 foot view with all kinds of fishes in it. It's up to you to think about it now.
So now , this what I think would be better for you and sor your fishes. As a fish keeper or as an aquarium hobbyist you have know everything about the fishes that you want to keep in your tank. Most of the people in the hobby add different kinds of fishes in their tanks which might be is their own way of fish keeping.
But as a hobbyist myself this is what I feel, when we are keeping any fish in our home in our tank we are seperating it from nature, this is the first thing we should keep in mind , so what you have to do is watch and learn about the natural habitat for the fishes you have, once you understand their nature try and create it in your tank .
This is the best thing you can do in your tank mate..you have cichlids, they have their own nature and personalities, try to choose one species of fish and create a natural scape for them . Lets say u choose to keep only oscars, you can add some more big rocks and also put in many almond leaves, I think this will give them a natural feel and they won't be much stressed when they get big coz Oscars move in small packs/schools. You also get Oscars in every color you want and u can keep even 6 of them in your tank.
This is what a good hobbyist will do for the fishes and will also be a good view to see how the fishes live in nature. This is good for you and your fishes mate.
Lastly if you want a mix species tank then you can keep the fishes you have ( 9 inc and 2x 6 inch oscars , a 8 inch frontosa 1 african snakehead 2 bichirs ( 1 senegal 5-6 inches and 1 delhezi 8-9 inches ) and 2x salvini chiclids) just return the sharks and for now u can add either 6 tinfoil barbs or 6 silver dollars and once the fishes grow big return them.
For all hobbyist - would be really helpful for the fishes if you research on the natural habitat and personalities of any species of fish you are keeping and try to give them their natural life.
PLEASE REMOVE FISH POOP ANS DO REGULARLY WATER CHANGES IN YOUR TANKS. HAPPY FISH KEEPING!