I agree with Nancy that you've dug yourself in a bit of a hole. Ten gallons will not support a bimac, especially with bottom-end filtration.
Here's what I would do: Pick up 3 30-gallon breeder tanks, buy or build stands for them. Get a 75 gallon stock tank from a farm supply store and set it up as a sump. Set up a drain in each tank "LFS-style," that is, drill a hole near the top, and use a PVC elbow inside the bulkhead (octo-proofed, of course). Have each drain into individual 3 gallon buckets of bioballs (or perhaps one larger rubbermaid) and then into the stock tank; and use a decent pump (Mag 9 perhaps) with the output split into the three lines, one for each tank. You're going to want a real nice skimmer in the sump, expect to spend about $600 on it alone.
Go around to different LFS in the area and see if they will let you borrow or buy bioballs out of their filtration system. That will jumpstart the system, and you might be able to move the octos there within a month.
In the meantime: water change, water change, water change.
This system IS going to take up a bit of space and a bit of money, but the bottom line is you've dropped the ball, you already have the creatures, if you want them to survive its up to you to find that space and money. If you're a little creative with a saw and a drill you could build a stand that will stack the tanks vertically above the sump and fit in a large closet or storage room.
Dan