Considering trying to build a sump in the future. No idea where to start.

Ok so I've read a little bit about it but cannot find a good technical explanation of the sump.

My 29g tank sits on a stand that is open on the bottom with a shelf about 4 inches above the carpet. The plan is to put a small 2.5 gallon sump down there and cover the lower half of the stand to cover it up.

Now the complicated stuff starts. I do not really understand how the sump flow works.

I would buy an overflow box like this: Reef Aquarium Filtration: Eshopps Overflow Boxes
The nano one has a max flow rate of 200gph....but if I get a pump that pumps water up at say 225...it could potentially drain the whole sump nd overflow my tank, right? How is this controled? What about if the pump looses power for some reason.....the sump would then overflow and the entire contents of the tank would flow into my sump!

Then I would run tubing down to the sump and have the water fall into one of those sock things. This is where I get a little lost.
Do I have to have separate chambers inside the sump? Can I just put a layer of sand in the bottom? How do I separate a small tank like 2.5 gallons into the three-chambers I see everyone using?

How strong of a light do i need on the sump?

My real fear, though, is I don't understand how to maintain the right water levels. How do I know how strong of a pump I need to return water to the tank? I'm terrified of the whole thing breaking and one or both overflowing everywhere. This absolutely cannot happen! haha

Is there some sort of ready-to-install nano sump system that I can buy?

This is a mockup I drew quickly.

How does this setup look?

Assuming a nano-overflow into a 2.5-gallon aquarium that has a max flow rate of 200gph, what size return pump do I need to work the water back out?

As I understand it, this basic setup allows water to flow from the overflow to the right side of the sump where a divider allows water only to pass underneath the divider, over the rock and up to the top of the chaeto. I did not include a light but there would be a simple desk lamp or something down there. I figured with the extra space on the left I can set up a simple auto top-off thing with the suction funneled into a 1 gallon jug of RO water that I will change out as necessary.

Is this basically how this sump would function?

Melevsreef.com | Acrylic Sumps & Refugiums
Read this. It will help with all your questions. He is a sump guru around here.

I will also try to help a bit. It seems your biggest concern is placed in the right area. What return pump? On every quality pump you will see a chart or a spec sheet that tells you that pump X has a max head pressure of Y feet. So if the distance from your sump to the top of the tank where your return line will go is approx 4ft(could be more or less so get the tape measure out) then you will need to see what the gph is for that particular pump at 4ft (or whatever your height is). A pump may say 600gph on the box, but that is sitting in a pool of water with no head pressure(gravity and the weight of the water). So at 4ft this same pump may only put out 200gph.
You want to make sure that your return pump is rated just below your overflow capabilities.
Also, is 2.5 gallons the largest sump you have room for. If your sketch is even partially accurate then you can put in a larger sump, and this will all be much easier to do. A 2.5g sump may not be worth all the trouble. Someone on here may have one that small and can give you some solid advice that I can't. I personally wouldn't go smaller than 5-10g and that would only be a 2 compartment sump. I would get as big of a sump as possible.

I also don't think a 2.5 gallon sump will make a difference. Remember, you can't fill the sump the whole way -- you have to leave enough empty space in it for the main tank to drain however much it is going to drain in a power outage. This usually results in people filling their sump 2/3 to 3/4 of the way. So that doesn't leave much water in a 2.5 gallon sump when 1/4 to 1/3 of it has to stay empty. Your return pump is going to take up space in it, and it's really too small to have dividers. I don't see the point... Go as big as you can fit for a sump -- there seems to be space in your drawing on the bottom shelf. Why not have a sump that fits the whole thing?

You should probably do a minimum of a 10gal tank under there, I bet it'll fit. That way you'll have more water to work with and more space for the equipment. Since the cabinet is open, you could make it a display sump/fuge, and add lots of pretty microalgae, and rocks. Or else, you could get some dark fabric and hang it over the front to hide the sump.

The most I could possibly do is a 5 gallon standard tank. I measured the space I have and I only have about 9 inches of clearance from front to back and a standard 5 gallon is 8.4" so even that is cutting it a little close.

How does that setup look? The difference in price between a 2.5 gal and a 5 gal is negligible so I would just go with that...but i don't want it to be a display fuge. I plan to buy some solid fabric and drape it like a curtain underneath the tank so that i don't have to see the sump or the 24-hour desk light.

My ideas for the actual sump, though, does that look like a good plan. The rock is under a stand that I would keep the chaeto on made of egg crates. I saw it while researching sumps and loved the idea and it looked so good when they did it. They put about 2lbs of live rock underneath the stand and then the chaeto on top of the eg crates. Said it makes it easier to access, gets it closer to the light, and avoids it getting stuck in the pump (which rests on the floor with the rock).

For example, either of these would fit...and the 6-gallon looks pretty nice:
[ame=http://www.amazon.com/T6401-Schuber-Wright-Beveled-Aquarium/dp/B006WP74L0/ref=pd_sim_sbs_petsupplies_12]Amazon.com: T6401: Schuber Wright Low Iron Glass 6 Gallon Beveled Edge Aquarium: Pet Supplies[/ame]
[ame=http://www.amazon.com/Carolina-Biological-Supply-Company-Aquarium/dp/B005VDO7QO/ref=pd_sim_sbs_petsupplies_26]Aquarium Tank, Glass, 5 1/2-Gal: Amazon.com: Industrial & Scientific[/ame]