one turtle died, one still living. ideas for care?

Question
i had two red eared sliders, about 7 years old, 4 inches in diameter. yesterday both were fine. today one is just an empty shell - no body, a couple bones inside.

a little background: we last cleaned the 10 gal aquarium 4 months ago. it is lit with a lamp and reptile bulb, filtered with a small in-water system, two moss balls to help keep the waste down. daily diet of one pellet/stick of TetraMin for aquatic turtles.

we are cleaning the aquarium. the other turtle appears fine, but we are wondering:
1 - any idea what happened to the dead turtle?
2 - is our other turtle now in danger of getting sick?

Answer
Hi Rob,

I'm half hoping this is a joke, but assuming that it isn't, let me go through the information you gave me and explain what the problems are and what you need to do to fix them.

1)  The tank:  10 gallons is much, MUCH too small for two 4" turtles.  It's really too small even for a hatchling.  It's roughly the equivalent of you sharing a very small closet with another person--with no ventilation, no cleaning, and no toilet.  Needless to say, this kind of overcrowding is very stressful and can bring on disease.

Fix:  A much larger tank, minimum 80 gallons.

2)  The filter:  I'm not sure what you mean by "small in-water system," but whatever it is, it's not enough.  There's no filter on earth that could adequately filter the water in a 10 gallon tank enough for a 4" turtle, and the moss balls don't really help.  Just because water looks clean doesn't mean it is.  Water in a toilet bowl is clear, but you wouldn't want to drink it.  Add in lack of regular (weekly) partial water changes, and the water quality goes down even further.  Poor water quality can lead to skin and shell fungus and infections, which can lead to systemic infections, which can lead to massive organ failure and death.

Fix:  A much better filter, along with the much bigger tank.  The filter should be able to handle double the tank's capacity, and by that I mean double an adequately sized tank, so for an 80 gallon tank the filter should be sized for at least 160 gallons.

3)  Lighting:  You didn't say what the basking and water temperatures are, so I'm guessing you don't know, and I'm also guessing that there is no source of UVB.  Without proper temperatures, turtles won't be able to digest food, and they won't swim and bask properly.  Without UVB, they can't metabolize calcium and will eventually develop metabolic bone disease (MBD), which can be fatal.

Fix:  Maintain correct temperatures of about 90 basking (surface of basking area under the bulb) and 75 water.  Use a quality UVB bulb--for heat and UVB combined, I recommend a 100 watt ZooMed Powersun (replace yearly).

4)  Diet:  I'm really not sure I'm understanding you correctly on this one.  If you really meant *one* stick daily and nothing else, it's really a miracle your turtles survived this long.  A general rule of thumb for pellets is to feed an amount roughly equivalent to the size of the turtle's head, for each turtle, daily for turtles under a year old and every other day for juveniles and adults--but that's *in addition* to offering other foods such as animal proteins and greens.  One stick per day is a starvation diet, and it's probably why your turtles were so small at 7 years old.  

Fix:  offer a good, varied diet that includes pellets, various animal protein, and greens/veggies.  I'll provide links below that will give you lists of good foods.  While adult turtles don't necessarily have to be fed daily, your turtle is surely extremely underweight and should be fed daily until he is healthy.  Don't overfeed, because you don't want him to grow too fast, but there's every change that within a few years he will double in size, given adequate nutrition.

As far as what happened to the dead turtle, there are any number of things that could have killed it, including systemic infection, MBD, massive organ failure, or starvation.  I strongly suspect that the reason there were only bones left is because the turtle died and the surviving turtle, starving, ate it.  And yes, the remaining turtle is in imminent danger of death.  Turtles are very, very tough, and it's a testament to their hardiness that they can take all kinds of neglect and still look "fine," but as I said it's amazing that both your turtles lived this long.

Here's some links that will provide more detailed information.  Read it all over, and if you have any questions at all, please post back.

http://www.redearslider.com/
http://www.austinsturtlepage.com/Care/caresheet-red_ear_slider.htm
http://www.austinsturtlepage.com/Care/care.htm
http://www.austinsturtlepage.com/Care/waterquality.htm
http://www.austinsturtlepage.com/Care/housing.htm