Blister

Question
My turtle has a blister on its inner leg I don't know what it is from or how to treat it.

He is a southern painted hatchling and is in a 55gal tank with another hatchling southern. the water is 78 degrees and I have a house bulb for basking a uva/uvb bulb its 5.0. a basking dock and a whisper filter and heater for a 60 gal tank.

Answer
It's not likely to be a blister unless the turtle has a chemical burn or you are using some kind of electrically heated basking surface. It's more likely to be an abscess ( infection ), or a parasite. I would recommend a vet, because not knowing what exactly it is, if you treat it the wrong way a more serious infection could result that may claim his leg, or his life. Especially with aquatic turtles, keeping any wound sterile is key to prevent serious life threatening illness.

I believe at my request they have added a attach an image option to the ask a question page. Perhaps you could get a good close up picture of this "blister" and follow up on this question. I would also ask you to include the brand of your UVA/B lamp when you follow up as it may be important.