What size tank would you go with?

[Delphinus]

I need some opinions..

Ok some background. As you probably know I currently have a 280g tank in the works, and currently as they wait patiently to be transfered, my fish are in a 5 year old cube (30"x30"x30") reef tank, about 115g in volume.

There are 3 fish that I currently have in the 115g whom I'd prefer not to transfer into the 280g:

- A pair of C. ulietensis butterflies. The 280g will be full reef and the butterflies have proven a little bit too destructive for that. But I really like the fish and want to keep them.

- A golden dwarf moray. 2 reasons, the 280g is an inwall with the top open into a tank room, and it's going to be too difficult to feed the eel the way it's setup.

My original plan was to move the cube tank into the tank room and keep the 3 in there. That's their home now, it would still be their home, everything the same except a much smaller bioload in the end.

But this poses a few challenges:

- The cube tank isn't a good fit for the tank room. It could go in the corner nicely, but the fact it has dual overflows means one overflow would be right in the corner and if anyone ever made it into the overflow, there would be NO way to get them out of there.

- I could cap off the overflow but then it's just lost space. Removing the overflow is obviously not an option since it's a running tank.

- Also, the cube tank is horrendously dirty after 5 years. 5 years is a pretty good run for a tank anyhow, it would be good to give it a good scrub down. But that too would imply needing a different tank for a temporary home and the question becomes what do I use for that, and if one were to consider doing that anyhow, why not consider just getting a new tank?

So that leads into the question of what would be a good fit. Currently I have in surplus the following tanks:

- 20g (2)
- 30g standard (36x12x16)
- 40g breeder (36x18x14)

I'm not sure I'm too enamored with using any of these, they're awfully small. The fish aren't huge but they're used to 30" of swimming room now. The 40g breeder would make a nice footprint but being shallow I wonder if that's not a little unkind to the butterflies.

So that leads into the question of, if I had to buy a tank anyhow .. what should I look for? Considerations are space and budget of course. I'm thinking of something like a 65g or a 75g tank (36x18 footprint) and using the steel stand I already have for the 40g.

Or am I foolish to even think of this combo in a tank together? I mean, they're all together right now but as a part of a much larger community, so I'm not sure how the dynamics would change.

Ahhh! Too much thinking for a Friday night. My brain hurts! ... But please let me know your thoughts. Thanks!!!