Cardio while on Cycle

I am currently running a test only cycle with 500mg a week.

My goal is to add some good lean muscle.

I want to know what the best form of cardio is while being on a cycle. As I am taking in a lot more calories than usual. I want to keep fat down and hold on to the muscle gains. How frequently should I do Cardio exercise?

Stats:

Age: 24
BF : +-12%
Height: 1.80
Weight: 79.1kg
Calorie intake: +-3800 a day

Program:

Mo: Back
Tu: Shoulders
We: Legs
Th: Chest and Triceps
Fr: Biceps and Calves
Sa: Here I've been doing some swimming. (I'm not a great swimmer so that's why I want to add more Cardio)

What generally works for me is 3x low intensity sessions a week, incline walk (10%) at 4.5km/h for 30min

Helps keep my metabolism firing too while keeping bf in check..

Keeping in mind its person dependent, some people require more, others less.. but use it as a guidline and adjust to suit yourself