Thanks so much for your reply.
Let me first add some observations, then I'll get to the requested information.
Her right front limb seems to be atrophied and completely useless. The color is also somewhat white, unlike the other limbs. I wonder if it is broken and even dying. Her left front leg seems also weak, but not as bad as the right front. Her hind legs seem normal and strong. She has maintained her robust weight. Her FBN tankmate for 35 years seems perfectly fine.
View attachment 88423
Figure 1: This is the sick/injured newt. Note the right front leg has lighter color compared with the other 3. It does not seem to work at all. The left front foot is somewhat weak also but she can move it at least.
For the past 36 hours, I've placed the sick/injured newt in a small 6" by 3" plastic tank with just enough water to keep her moist but not enough for her to drown. I include a photo of this. The main tank in which she has been living with her tank mate for all these 35 years is 12" by 6" with smooth rocks to climb on. I attach a photo of this with the remaining newt.
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Figure 2: This is the healthy newt in the larger enclosure. Photo from the top. Tank 12" by 6" with water depth 3.5"
For over 30 years, the water has always been just plain tap water, no filters or anti-chlorination. Temperature is inside-ambient, typically 65 to 73 degrees F. Lighting is only from inside the house, no UV or special lighting.
I feed them almost exclusively live tubifex worms that I rinse and make sure are fresh prior to introducing to the tank. I provide enough so the worms live among the rocks and the newts can forage for them over the typically four weeks until I carefully clean the tank and refresh their food supply. Only on the extremely rare times (twice per year, typically) when I can't get live tubifex worms, do I use commercial feed pellets (HBH Newt and salamander Bites) or freeze dried bloodworms. They prefer the Newt Bites to the freeze dried worms, but the sick one didn't like either alternative much.
I've read (on your site, I think) about sometimes the need to amputate a limb if it is infected or perhaps damaged. Part of the skin around the most withered front leg looks white. It is very thin. I wonder if this is what we should do? I will see a vet tomorrow afternoon (about 28 hours from now).
Thanks so much for your feedback and kind assistance!
Best regards,
Newts100