Although chain pet stores claim to be the pet experts, they are decades behind on guinea pig care. It is not recommended to buy any of the following items from a pet store for guinea pigs.
Anything with seeds, grain, or dairy
Seeds are a choking hazard and way too fatty for nutrition. Guinea pigs cannot digest grain or dairy.
Pellets that look tasty to you (colors, seeds, and dried fruit).
If it looks good to you, it’s not good for them. Dried fruit is too sugary to be part of their every day diet, seeds are choking hazards and are too fatty, and color additives can contribute to guinea pig stones and health issues. Instead, look for a pellet that is Timothy Hay based with no fillers. See “What pellets should I buy?”
Exercise ball.
Guinea pigs’ fragile backs are not meant to concave to fit inside a ball. Additionally, being trapped inside causes stress and anxiety. They’d rather run freely in a play pen.
Harness or leash.
Again, guinea pigs have fragile backs and they can wiggle out of anything. They should not be going on walks outside. Set up a playpen instead!
Vitamin C drops.
Never put vitamin C drops in guinea pigs’ water. Vitamin C deteriorates when it hits light, so the product is immediately useless. It also affects the taste of the water, which discourages drinking water. The best way to give them vitamin C is to feed lots of fresh veggies! A ¼ of a bell pepper contains 2-3 times the amount of vitamin C a guinea pig needs. See “How do my guinea pigs get their vitamin C?”
Let’s explore more about guinea pigs:
Guinea Pig Care Center 