After our nano top almost caught fire (I happened to spot the blue burn going up the wire and got it unplugged before there was real trauma) we found a great all glass top that fit our model and a super price on a halide/pc leg supported light. We kind of think the light was mispriced as we have seen it a few times at about 3x what we paid but if you can find A glass top made for your tank, you might want to consider buying one. Ours was 2 pieces and we used a silicone hinge to keep them together and still be able to open it. It was not very expensive and fit perfectly.
How did you secure the glass to the tank?For an octopus tank, you should be able to find an inexpensive LED setup. I have a couple (found on eBay) that have very simple wire legs that only raise it off the tank enough to give airflow to reduce heat. I have to move these to open the lid (my attempts at attaching them to the outer cover failed after a bit) but they are really not much of a problem. With the nano cover, you could likely place them behind the front opening and leave them there.
Octos will do just fine with simple room light (ie no tank light at all) but anything else in the tank will need more.