A little something to keep in mind about North American Box Turtles - in some states of the US there laws regarding ownership, breeding and sales of box turtles. It is a good idea to check out your local laws about keeping animals, birds & reptiles that are defined as "wildlife".
http://aboxturtle.com/state_laws.htmhttp://www.wildlifedepartment.com/turtles.htmI am going to echo the warning about washing hands after handling. (And drive that point home if anyone in the home has any type of illness that compromises their immune system.)
A note on the diet - it will take more than fish food. A young box turtle (and anything under 4 inches is YOUNG) has nutritional needs that include certain vitamins & minerals.
In the wild turtles eat: snails, insects, fungi, berries, slugs, worms (especially earth worms), flowers, fish, roots, frogs, salamanders, eggs, birds & even snakes (depending on size of the turtle). Turtles also will eat on carrion when hungry enough. Young turtles are primarily carnivorous during their first 5 years of life, while adults are more herbivorous - though they eat little green leaves. The young often hunt in water while adults hunt on land. In Zoos - turtles are often fed salad, earthworms & crickets (and an occaisional mealworm). There are also some commercially prepared pellet diets. When fixing salad greens - remember that iceberg lettuce has no nutritional value. Veggies include: carrot, kale, dandelion greens, romaine lettuce, wheat greass, turnip greens, fresh mushroom, squash or zucchini bites, other veggies, peas, sweet potato,a bite or two of beet, broccoli (as a treat), beans, pumpkin and they also like fruits (most berries) apple, cantalope, chopped grapes, figs, peaches, cherries, kiwi, banana. Also offer some sort of calcium - you can purchase a powdered supplement to sprinkle on food and try boiled egg shells & cuttle bones. Calcium deficiency is one of the top causes of illness & death, as is Vitamin deficiencies (A, C, D & E)
You can also offer feeder fish, chicken, wet cat food (in small quantities), boiled beef heart, waxworms, sow bugs, beetles
Housing a turtle - a better option to a glass aquarium is a rubbermaid tub & specially constructed wooden enclosures because of the sides. If you go with a glass aquarium - block off the sides. Turtles startle easy when things suddenly move in a room and being surrounded by glass with no escape can be very stressful. They also see the space beyond the glass and can spend a lot of time and energy trying to get out through the glass. In the wild, they do tend to stick to environment that hides them and seek out places where they can protect themselves from predators.
Soil is good but you may want to add a bit of sand & leaf mulch (and even sphagnum moss) and mist it each day. Give them an area in the enclosure where they can burrow under the soil and offer logs or cave like areas to hide. Also provide a few flat rocks (this helps them keep their toenails trimmed). They also like an area of water to wade in (and sometimes use their water dish to poo in...so check it and change it often). You can also offer a deeper area of water with access to land for them to swim. In warmer months - an outside enclosure with this might be a perfect solution. The water must be warm though - cold water can disable them. Also best to supervise the swimming sessions and make sure they dont tire themselves out if they swim. Some will swim & some will just soak in shallow water. During colder months you can offer them this as an enrichment activity.
Turtles require humidity. Dry air can cause eye irritation & respiratory illnesses. Turtles tend to eat after being misted too. You can fix a bottle of warm water & mist the environment each day. (In the wild, they are most active at dusk and dawn because of the dew content). You can also add potted plants into their environement to help retain humidity.
Turtles also require a full-spectrum light and it is necessary to have that or sunlight for Vitamin D production. Temperature range is to allow both a warmer & cooler side in the enclosure - 85-87 on the warm side & 75-78 on the cool side. If it is too cool - a turtle will become inactive.
Hope this helps...