Getting the Light Suit will be pretty quick, but it's the last needed upgrade and all of Aether and Dark Aether (except for the finale) will be reachable after we get it. So much of this page and the following page will be devoted to gathering up all the remaining expansions.
Main Energy Controller
Return to the Great Temple, enter the Main Energy Controller, and talk to U-Mos. He just up and gives you the Light Suit for all the work you've done so far. There's still more to do though since there is still a Dark energy controller in the Sky Temple.
The Light Suit gives you total, not partial, immunity to the effects of the atmosphere on Dark Aether. Is also protects you from some other environmental hazards such as the poison water on Dark Aether. You can still be damaged by Phazon however.
Expansions (Temple Grounds)
As mentioned above, there are quite a few expansions still left to get. We'll cover the ones here in Temple Grounds now, and the rest on the next page.
Get to the the Sacred Path; if you've just talked to U-Mos then it's just at the other end of Transport A. Locate the portal on the high ledge here and go through.
Expansions (Sky Temple Grounds)
First deal with the Pirates who've decided to guard this place. There is another Sonic gate here where the lift to the temple is located in the Light version. There are emitters located on either side, and a third one inside an alcove a little distance away; the combination is Alcove, Right, Left, Alcove. When the gate opens you get the fourth and final Beam Ammo Expansion. You don't need the Light Suit to get this, but it's much more convenient when you have. With the last Beam Ammo Expansion you can now carry 250 Light and Dark ammo each.
Before going back to the Light world, continue through the door here.
There is a Dark Metroid here, and at this point in the game the easiest way to deal with one at close quarters like this is to drop a Power Bomb when it attacks. Grapple or Screw Attack over the Phazon to the next area.
There are more Dark Metroids here and there are too many to get them all with Power Bombs, but as long as they are at a distance a charged Dark beam followed by a missile is still best. You'll want to get all of them, including the ones floating around off the cliff. The expansion we're looking for is in a nook in a pinnacle of rock off in the distance as you look over the edge. You can either use the Screw Attack to reach it, or switch to the Dark Visor and hop the invisible platforms. Note that you can get this expansion any time after getting the Echo Visor, but, what with fighting Metroids and the lack of safe zones, it's probably better to wait until later in the game. We will be coming back this way again in the hunt for Sky Temple Keys, so if you know what you're looking for then continue on to save a trip, but in the interest of keeping the Key material together we'll save that for later. Get a scan of the Ingclaws as long as you're here; they are just like the regular Ingclaws except they don't happen to be spewing toxic gas.
Expansions (Temple Grounds)
Fortress Transport Access
Back track to the Light world and continue to Fortress Transport Access on the way to Sanctuary Fortress. Look for a bright yellow column of light about half way through and step into it. Now that you have the Light Suit, the light acts like a transporter and takes you to a hidden room. Grab the fourteenth and final Energy Tank there and step into the light again to get back. With this last expansion you now have 1500 energy units, up from your original 100 units.
We'll continue on with the Sonic Boom and the last few remaining expansions next.