I have a Red Sea Max 250 -- which is the older version but I believe similar-ish footprint size. Its about 17-18" deep due to the AIO structure. I've had the tank for 5 (?) ish years.
What I have right now:
- Flameback angel
- Yellow coris wrasse
- Ocellaris clown pair (2 fish)
- Tailspot blenny
- Neon goby pair (they hate eachother)
- Yasha Goby + pistol shrimp
So thats 8 relatively small fish, and I feel like that is the sweet spot for my tank's capacity to handle the bioload.
I'll also add this opinion. The tank is borderline too small for the angel. It 100% demonstrates some neurotic behavior where it does this figure 8 lap around the back of the tank at various points in the day. Every other fish is 100% fine -- but that was intentional. The Angel is the real active swimmer, followed by the wrasse. Nothing else is active. Everything is fairly peaceful, again, by design. Angels are active open water swimmers though -- the wrasse is active but its active via hunting the rocks, not trying to swim laps around a 36" long tank.
In the past I've had a blue star leopard wrasse, Pygmy hawkfish, Banggai cardinal, carpenter's wrasse, clown goby, yellow watchman goby, multiple fire fish..
My personal preference always leans heavily to lots of small fish vs few larger fish.
Also another opinion, which is not really a hot take, but people do put yellow tangs in these tanks -- based on my experience with the angel, its way too small.
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Oh and grats! When i was getting ready to move this tank I was on the fence about upgrading to the Reefer series -- really clean tank.