Entirely too little pay for how much work they demand from PetCare Specialists, that's actually probably the biggest problem with PetSmart (cannot speak for PetCo, but I doubt it is very different).
I worked there for six months before I got burnt out. There were some issues with some animals having to be euthanized due to neglect from some of the employees, but most of my burn out was them taking advantage of a minimum wage employee who was willing to work and work well.
In 2010/11 (whenever it was) employers were still allowed to work a "part-time" employee 39.59 hours a week and still claim them as "part-time". That is what happened to me. I was basically working full-time hours but getting none of the benefits for it and only making a piddly little 7.75, or whatever it was.
I most often worked in the mornings opening the store, here is everything I had to do:
6am-9am (everything to be completed BEFORE the doors open) Mon-Fri.
-Come in and clean out the bedding/cages for either the Small Animals, Reptiles, Birds, Quiet Room/New Arrival Room or receive massive orders for the Fish Tanks depending on the day (for the record, being able to clean out all of the birds within two and a half hours is doing it fast). It should also be noted receiving fish is the only thing a manager EVER helped me do in the morning at that store.
-Check on all animals in the Quiet Room where sick or injured animals are housed. Write down observations, give medication.
-If someone is ready to be returned to the floor, do so.
-Clean and sanitize all hides, toys, water bottles and food dishes.
-Feed and water them.
-Check on all animals in the New Arrival room, move animals ready to be put on display out to the main floor.
-Clean and sanitize all hides, toys, water bottles and food dishes.
-Feed and water them.
-Check on small animals, clean and sanitize all hides, toys, water bottles and food bowls.
-Check on birds.
-Spend time working with any conures (manual states at least 20 minutes a day) available to keep them sociable since they are often quite young (generally I'd just put them on my shoulder while I move around and do what I need to do with the other birds).
-Clean and sanitize all toys, water bowls and food bowls.
-Check on reptiles.
-Clean and sanitize all food bowls and water bowls, spot clean waste (unless Thursday when full cleaning is done).
-Take all dirty dishes and put them in a giant sink to sanitize in a solution. Pull out replacement dishes and fill them with food according to species.
-Cut up carrots to give to small animals.
-Cut up grapes, sweet potatoes, carrots and apples into diced pieces for birds.
-Feed everyone including reptiles who get pinky/hopper mice (depending on the day), crickets, meal worms and feeder fish. Fish are also fed flakes and/or blood worms.
-Clean (vacuum and replace decorations) a specific set of fish tanks on a given day.
-Organize the plant tank and make sure the snails are fed as well.
-Drain the sanitizer from the sink and set all the dishes out to dry.
-Open the store.
From 9am - 12pm
-I was alone until a swing shift came in to handle the entirety of PetCare. That meant I was getting crickets, feeder fish, fish, small animals, birds, etc. etc. while also advising people on products and husbandry.
12pm was generally lunch. 3pm I went home.
All of that for 7.75 an hour. I probably had to do less garbage managing a pizza joint for more pay.
In the end, they just took advantage of me considering I was hired on "just for 12-15 hours a week". After my first week there, for the six months I stayed, there was not a single week my hours went under 36 hours except for when I was in the hospital.
The work was exhausting and there was just little yield for it. Couple that working with other people who have no knowledge on the animals they are caring for and who regard a hamster's life as "just a hamster" and it's not somewhere worth working for.