Electric blue acaras are not half electric blue ram. I don't know where people get this idea. They would look very different and probably not get the exact same size/proportions as normal blue acaras if they were. I don't know how you'd pull that off anyway, you'd probably kill a ram trying to get milt out of it to fertilize JD eggs because a fish that size is not hatching out of ram eggs.
It is just a recessive gene like the blue gene in electric blue jack dempsies, when you breed them to normal blue acaras the fry come out looking like normal blue acaras. I don't know why people don't think the same gene can't pop up repeatedly, when we have electric blue jack dempsies, blue diamond discus, thai silk flowerhorns, and arguably honduran red points (also a recessive blue gene). The electric blue gene in rams doesn't even behave the same, it's incomplete dominant, crossing them to normal (or any other) rams makes weird purplish fish with a large blue patch and bigger face spots.
Also apistos are polygynous. Females will chase males off once eggs are fertilized and he will go spawn with another female. Might as well get multiple females at that point but he does not seem keen on breeding, so I would honestly say a few males of something like cacatuoides would be fine in a 75... given we're going the amazonian route.