At minimum I assume 1/2" glass due to how much water it can hold. Like many have said, the MP10s are rated 3/8" thick but plenty of people have said they will work on 1/2" but to be safe use the cable tie/mount kit to prevent it from getting knocked off. It would be a nice combo IMO as you can have one on the side and the other on the back wall, have them alternate so the waves clash.
Safe bet would be the MP40, many as well have said one is more then enough for their tanks. Maybe an MP40/MP10 combo?