small fish recommendations

[OrionN]

I think you fish load is a littel high with large fish. I would remove one of the big three, but everybody is different. I am sure you can keep them thriving.

Small fish that I like are:
Royal Gramma. You can keep a harem of them in your tank. Maybe three in the 90 g tank, they will breed in your tank, colorful and nice interesting behavior. If you don't feed them a good diet their color will fade a little. If you go this rout you need to get small ones that keep together in LFS. Male RG will kill each other and they turn male very quick if stay alone for any length of time. Best to have LFS put them together on arrival and they should be fine. Get the smallest ones you can find. They should be fine with the rest of the fish in your tank, even with a mean fish like 6-line.

I love Marine Beta. On in your tank is great but they are secretive and only after several months you will be able to enjoy his beauty.

Mandarin is a great fish but it will have problem with you six-line. Donot kepp Mandarin with 6-line.

If you have a sand bed, one of the shrimp goby is very interesting. Which one is up to you.

One or two of the jaw fish, even the yellow head Jawfish, are very beautiful and interesting fish.

Orchid dotty back are grate fish and should also do well in your tank. Color fad is a problem unless it get good diet. Can keep pair that will breed

I would avoid clown goby in a SPS tank. They will kill a patch of SPS to make a nest and this can potentially cause death of the colony.