I've heard that it's fine. I've used it before without any issues but I've never used it long term because it starts to stink really really bad. I'm pretty sure it's very high in protein so you might want to include more things like fruits for vitamins and moisture.
I have heard of many people using fish food, but that they say the crickets stink even worse when feed the fish food.
I use chicken feed and its $15 for a 50lbs bag. If you use it a lot then I would say get the big bag, but if not, dog food is also a good source of food to use.
I bought the 50lbs bag of crumble chicken feed and use it for the crickets, mealworms and superworms and have used only 1/4 of the bag in 2 months.