young map turtle with a white bump

Question
We have a young map turtle who has developed a raised white, pussy looking spot on his foot. He is eating and acting the same as normal, the spot has been there for a few days.
He is in a 20 gallon tank, no substrate, his basking area is kept about 85 and his water is kept around 72-74. His mainly fed commercial floating sticks, and a few times a week a leaf of romaine lettuce and a higher protein treat. he is the only turtle in the tank, and i do water changes once a week.

Answer
20 gallon is pretty small and is going to cause a lot of waste build up, and in turn breed possible pathogens. A 20 gallon is ok for a hatchling, nothing more. You need at least a 30 if he is 2-3 inches long, and larger still if he is any larger than 4 inches. Aquatic turtles put out a lot of waste and in an unclean tank this can breed everything from E. coli and Salmonella, to various pathogenic fungi that will attack the skin, shell, and eyes. As he gets full grown you are probably going to need something on the order of 75-100 gallons, or an outdoor pond of a hundred gallons or more. Though they don't always get as large as fully mature sliders, they are much more jumpy, and need more room than an equivalent sized slider.   

You need bio-filtration rated for about twice the size of the tank. Water changes are not enough unless you are disinfecting and cleaning the tank of all growth as well every time, but that subjects the turtle to possible harmful trace chemicals.

You should also start with conditioned water, not tap water.

This turtle also needs a dry basking area that he can climb up on and dry off.

Since you say "about" when referring to temperatures, I don't know if you are guessing or not, but most people are guessing when they say "about". If so, then I would caution you not to guess, and buy thermometers. You'd be surprised how far off you can be on a guess.

The diet needs some improvement. Commercial floating sticks should not be used as a primary element in the diet, only supplemental. This turtle should be getting fed more fish, chicken, liver, shrimp, crickets, earthworms, and other fresh invertebrate prey. Romaine as a treat is ok, but it is not nutritious. Try some greens, grated squash, and other veggies. He may also enjoy occasional tomato and other small amounts of fruit.    

Map turtles are less tolerant of poor water quality than some other turtles, and they are a nervous species. This may lead to them bumping around and hurting themselves. That together with the captive stress in a tank that is too small, in high traffic areas where they are disturbed and stressed all the time, along with the less than ideal water quality in a tank that is too small and unfiltered...may lead to a case of fatal systemic infection. I think this abscess should be looked at by a veterinarian because skin infections in aquatic turtles can quickly get out of hand and turn fatal due to the nature of living in the water they void their waste in. Until you see a vet, you can drop in the recommended amount of triple-sulfa aquarium antibiotic, but I wouldn't let this go more than a week or you may be dealing with a more serious situation. I recommend you use only the sulfa based and not tetracycline or other which are meant for ornamental fish.

Clean and disinfect the tank with 1:9 bleach/water, rinse completely several times and refill with conditioned and dechlorinated aquarium water. Put the turtle in and add the sulfa, letting it sit for the recommended number of days in the tank; then do another water change if necessary and turn on the power filters. Do not run filters with antibiotic working in the tank. Repeat if necessary as provided by instructions, but this is only a temporary measure until he can be seen by a vet. A topical treatment of antibiotic in this case is unlikely to cure him completely in the underlying tissues, and it will probably return more vigorous without systemic antibiotics.

You ALSO did not state that you were using any UVB lighting. UVB lighting is MANDATORY if you are going to keep a reptile, otherwise their health will be compromised, especially in young ones.   

Note: Do not allow vet to administer vitamin A injection without serum retinol test, OR Baytril injection that has not been properly diluted, NOR any injection other than hydration fluids in the rear half of the turtle.       

    

http://www.chelonia.org/articles/graptemyscare.htm