You can take Fundies in a single tank and without a canister light. If you do, no matter how well you do on skills, you will get a "rec" pass. This means you are not cleared to go on to technical instruction with the agency yet. A "rec" pass can be upgraded to a "tech" pass, if you do a checkout dive with an instructor in doubles and with a can light, and perform to standards.
If you take the class in doubles, you must achieve a certain score to get a tech pass. If not, you are sent off to practice and come back for a reevaluation. I believe you have to get a 4 on all the core skills, but this could be wrong, and if so, I hope someone corrects me. The standards for buoyancy variation and deviation from horizontal trim are tighter for a tech pass. A tech pass clears you to go on to Tech 1 or Cave 1.
The Rec Triox class has been an odd man out in the sequence, because it, too, can be taken in a single tank, and you don't have to have a tech pass from Fundies to take Rec Triox.
Hope that information is helpful.