I've been using the regular Mazuri rodent diet for my rats and my mice and they've all been thriving on it! I've got an order in for some of the 6F from the local blue seal feeds that should be coming in soon. I'd probably try the Harlan since that's what Kara at NERD (who I got my rats from) feeds her huge colony of rats but I can't get it from anywhere around here as far as I know and I'm certainly not going to order $1000 worth of it! However, with the Mazuri I've noticed that their urine and feces do not smell hardly at all (I also use a mix of woody pet and aspen which helps) compared with the Kaytee lab block I was feeding before I found a place to get Mazuri locally. IDK I guess it just comes down to availability and personal preference to a degree. I know my rats are healthy and breeding well on Mazuri so I'm gonna stick with it!