Not really a serious DIY, just a simple modification. I thought I'd throw this up in case anyone else is looking for a inexpensive lighting option for a 40B or other 36" tank.
I had on hand an old 48" shop light I was using on my 75g before switching to T5. I found some 36" bulbs in 6500k at my local Lowes. After not being able to find a suitable fixture for those bulbs, I decided I would make my old fixture work.
So I got the bulbs and once home, I disassembled one end of the shop light. I installed the bulbs so that I could get a proper measurement where the end-cap needed moved to.
Marked the fixture, took it outside and drew a straight line all the way across.
Using my angle grinder and a cutoff disc, I made short work of the fixture. Don't forget to wear your safety glasses.
Fitted the end-cap and a few pop rivets and it is nice a secure.
Cut the wiring down to length, soldered the connections, and used heat shrink tubing to make sure the connection was good.
Finally, installed the bulbs and fired it up.
So there you have it, a little DIY, less than $20, and you can have a decent medium level light over your 40B.