will this work ?
 

I have a 100 gallon tank 5 ft long so its not that deep it has a fluval 405 and i was going to add a fluid sand bed filter and a protinen skimmer with the live rock the tank is not drilled and im not to sure how to tell if i can drill it.i am wondering if this setup will work for a saltwater setup without a sump or am i better off going with a sump ? please and thanks

I'm just a rookie at this, but I would say go sump, a tank that big would, IMO do better. You don't have to drill the tank if you don't want to, you can do an overflow box and plumb it to the sump. That's what I am planning on doing with my 72.

sump

sump
 

how do i know if i can drill the tank or not it is about 6 years old how do you tell if its temperd or not

If you're able to determine the tank manufacturer, that's a good starting point for knowing if the glass is tempered and which parts, bottom, side, etc. There is another method using polarized sunglasses and an LCD screen with white screen behind the glass you're trying to check. There should be a distinct change in how the screen looks when you rotate it or the sunglasses if the glass is tempered, generally a pattern or lines will become evident. If it is not tempered, there will be no change in how the screen looks.

+1

Most commercially manufactured tanks are tempered glass on the bottom only, but I would still locate the manufacturer if possible.