Going from canister filter to sump

[H2Orchard]

Ok y'all. New tank and new to saltwater. I got this 33 fluval tank with a canister filter. I attached a picture. I would like to build a sump for it. Since there are already holes in the tank for the intake and export of water would I need to drill new ones? What size of sump would be good? I've just keep hearing that having a sump is easier and better.
You can hopefully see the tubes in the back that goes through the filter now.

 

[Ron Reefman]

There are a variety of possibilities. I just built a new tank and I drilled 5 holes, a durso drain, a full open drain (with a gate valve) an emergency drain and 2 returns from the sump to the tank. I would never consider another tank without an emergency drain.

You could do a durso drain and an emergency drain and run the return from the sump over the back glass of the tank.

My old 40g cube was set up that way. You can see the returns running up and over the back glass (tank on the right).

My replacement for the above tank is this one. Left to right are: return, full drain, emergency drain, durso drain and return. Even I was surprised at how absolutely quiet this system is once it's balanced. And that's easy with a gate valve on th efull drain and using a multi speed return pump.