Eh, just put them into your 90 until you have a school of blue tangs, they'll be totally happy in there. It's at least an 18x tank upgrade!
But the mud on the bottom is kinda nice actually. It's a 'hey, that looks like a more natural little biotope' kinda nice. Pretty reefs are awesome for sure, but once in awhile it's really nice seeing something that stands out, especially something that looks like a natural biotope.
My local aquarium has some spotted bay bass that live in our bays. They live in a biotope complete with docks (where they hide in their 'natural' habitat) and trash. Yep, trash. I think it's their own little jab to make visitors pick up trash on beaches and bays. But you can't deny, that's a totally accurate representation of our bay... Well, once they plumb the bathrooms into that DT it will be totally accurate at least.
Got a 135 now. But I don't like hippo tangs.