dipsydoodlenoodle
Fish Gatherer
What do you have in the 10 gallon Dipsy? Could the occupants be moved into the 45 gallon safely? If so then you could then use the 10 gallon for the betta which would save you having to buy another tank.
If the 7 doesn't come with a light you can get clip on ones that hang over the tank. Arcadia do one, and there is also another type I've seen on Ebay. Can't recall the name but type in "clip on aquarium light" and you should get several results.
I couldn't really mix the tanks unfortunately.
I have goldfish in the big one; newts in the 10 gallon and shrimp in the 1 gallon (the shrimp were in with the newts but it was more the newts didn't like the shrimp - everytime one jumped the newt jumped twice as high - haha).