I think that looks like a big enough cage for 3 rats, especially if two of them are neutered boys
Ooh you should get some cheap plastic baskets and zip-tie them to the sides so they have more room to climb + great sleeping areas
tube hammocks are great, you can use them like ramps to each platform if you want 
I've put a flat hammock in the corner of the cage pulled tight, and used it as an "added platform" to give more walking/roaming space, my younger boys loved to roll around on it and tussle ^_^
Good luck with your new addition!
Ooh you should get some cheap plastic baskets and zip-tie them to the sides so they have more room to climb + great sleeping areas
I've put a flat hammock in the corner of the cage pulled tight, and used it as an "added platform" to give more walking/roaming space, my younger boys loved to roll around on it and tussle ^_^
Good luck with your new addition!