Is my Russian tortoise's indoor habitat the proper size for him?

That hinge on her plastron (bottom shell) is normal. It is supposed to appear "split". That allows her to close up securely when she retracts her head. These turtles do not get as big as other species, but a 10 gallon tank is too small. She also needs a UVB light source. Windows will block most of the sun's beneficial rays. You can find a UVB light source in most pet stores. A popular brand is the ZooMed ReptiSun light. They are good eaters, eating a wide variety of animal protein, plant matter and commercial diets. The link below leads to a care sheet providing additional information. http://www.reptilesmagazine.com/Three-toed-Box-Turtle-Care-and-Information/

Check environmental parameters first. Make sure the relative humidity level is correct. For Russians, it can range between 40% and 60%. Provide adequate UVB lighting. If the bulb is more than 6 months old, replace it. Provide a balanced diet including vitamin and mineral supplementation to promote shell health. Survey the enclosure and remove any sharp rocks or furniture. These can cause small scratches which can lead to infection. You can gently clean the shell using a diluted Betadine or chlorhexidine (Hibiclens) solution once or twice daily. If there is no improvement in the shell condition after 5-7 days, consider an exam with your veterinarian or a vet experienced in treating reptiles. You can review tortoise care at the links below. http://www.reptilesmagazine.com/Care-Sheets/Russian-Tortoise/ https://www.petcoach.co/amp/article/russian-tortoise-habitats-how-to-create

I suggest you refer to these links for information on proper feeding and husbandry. ( http://www.reptilesmagazine.com/Care-Sheets/Russian-Tortoise/ ) ( https://russiantortoise.net/russiantortoisediet.htm )

What you have appears to be an aquatic/semi-aquatic species of turtle. Basic requirements include a tank of at least 10 gallons initially, a water heater, a water filter, a basking area out of the water, a heat lamp and a UVB light source.

Romaine lettuce is not optimal for health or growth. Russians need a high fiber, low protein and calcium rich diet. Variety is key. Dandelion greens, kale, collared greens and turnip greens are recommended over romaine. Fresh, chopped vegetables should be offered and a commercial tortoise pellet can round out a balanced diet. UVB lighting and a heat source, along with calcium and vitamin supplementation, are also required. The shut eyes ma indicate infection or vitamin deficiency, namely vitamin A. Increase enclosure temps by 5-10 F temporarily to aid in recovery. Soak him in a warm 50/50 solution of water and unflavored PediaLyte for 30 minutes daily to maintain hydration or to treat or prevent minor dehydration. Have Squirt examined by your vet or an experienced herp vet to diagnose eye infection or injury. You can review additional care information at the link below. http://www.reptilesmagazine.com/Care-Sheets/Russian-Tortoise/

Check the temperature in the enclosure. Low temps can affect appetite in reptiles. He could also be a bit stressed by the change in environment. Soak him in a warm 50/50 solution of water and unflavored PediaLyte for 20-30 minutes. This will warm him up while providing hydration. Dice greens and vegetables finely to make eating easier.

We need more information in order to help you. Please post again with the breed of this turtle (is it a turtle or a tortoise?). Photos of the turtle's head. Photos of the cage set-up you have. Thank you.