I noticed a subcutaneous formation on my pet's side. Has anyone encountered this?
What's it? Is it dangerous? After feeding, it becomes more noticeable.
That was a week ago:

So now:


The frog is 13 years old.
Tank 30L, temperature 23 C, water replacement is made with standing water (more than a day). There is no filter. We change the water every two to three weeks. We feed them with bloodworms, never gave vitamins. The size of the frog is about 7 cm.
What's it? Is it dangerous? After feeding, it becomes more noticeable.
That was a week ago:

So now:


The frog is 13 years old.
Tank 30L, temperature 23 C, water replacement is made with standing water (more than a day). There is no filter. We change the water every two to three weeks. We feed them with bloodworms, never gave vitamins. The size of the frog is about 7 cm.