Well I actually ended up with a 50G tank, not 55 (that one was tempered, so no-go). The 50 is the same width as the 30, conveniently, so won't even have to modify the lights! 18" wide vs. 12".
Edit: To clarify, it's less of a stand and more of a DIY piece of furniture. My friend gave me the 'surface' his tanks used to be on - 8'x2' welded aluminum frame topped with plywood, finished in pine veneer/gloss. For reference the aluminum frame on its own weighs about 80lbs - heavy duty indeed. I will post pics at some point when time allows. Suffice it to say I'm able to fabricate whatever stand is required.
Okay, I will try to fit rebuttal questions on the same numbers you used
2. I am actually planning to go 'tunnel through' the overflow box, if that makes sense.
3. Both sides of the tank will be 'viewable', so ideally I'd keep all the piping the same colour, but haven't thought this far ahead yet.
4. Yes, it is!
5. Now that I have the 50G and 18" width, internal should be fine.
6. Yes, BeanAnimal's design thread (150 pages...) has references to keeping the depth only as deep as necessary to fit plumbing, similar idea to width.
7. Great point about having a return pointing under the box, would not have thought of this!
8. Yes, I've read that calling a number of glass shops is best, thanks.
9. I thought about that, but I think glass will end up looking a little more professional, no?
10. Good point. I have a number of submersible heaters, and now with using the 30G as a sump, should have plenty of room.
11. Yep, part of my calculations.
12. Yeah, going to try and get everything as level as possible. Going to be extremely difficult due to how uneven the floor is.
13. My drains have to be submersed, but sounds like either way will work, and both are not required at the same time.
14. This part I'm still uncertain about - the sump design. Will expand below.
There seems to be a number of different methods for bio-filtration, or rather how it's implemented. Also a number of different types of media. Let me try and explain my plan a little more clearly. It will be laid out in a progressive/linear fashion.
1. The drains will be coming out the center of the tank and down, then over on an angle to the left (if you are facing it) side of the tank
2. Drains (Primary siphon, secondary siphon, emergency siphon) enter chamber#1 below water line
3. First area fills and flows over through foam and into chamber#2
4. Chamber#2 filled with pot scrubbies acting as primary bio-filter
5. Water flows over into chamber#3
6. Chamber#3 houses refugium/breeding area (??)
7. Water flows through sponge (fail-safe filter prior to pumps) over into chamber#4
8. Chamber#4 contains pumps/heaters/return lines
Key design point is that the water always has the option to overflow if the chamber gets blocked.
Crappy paint diagram (Brown = sponge/foam, Green = ideal water level):
Does that clarify what I'm thinking? Thoughts?