Does anyone have a old dog that has darkstuff between the pads stuck on there feet. I have soaked in fungal/disinfectant rinse I got from vets and cream them with bepathen at night but he doesn't like to walk and this is the reason he is now fouling in areas he never use to
I have been to vets twice and they only look for about 5 seconds and don't really do anything to investigate what the substance is

I use salt for a lot of different doggy ailments if I am not 100% sure what they are.
It can't hurt and if it works then well, bonus.

I would try doing salt soaks.
Salt kills bacteria and helps dry out wounds. Fungus loves moisture so by removing that, you stop growth.

Just use a shallow bowl, half fill with water and add a teaspoon of salt.
Lift the dogs front end up and drop his foot down in the bowl.
Get him to stand there for a while (as long as you can, but even 10-20 seconds is beneficial.
Dry thoroughly (use a hair dryer is possible) and repeat 3-4 times a day.

My MIL's dog had an infected toenail and it cleared it up really fast.
I have also done this on hot spots on my boys head, just bathing with cotton balls.

I'm not saying it will cure it, it may not make a difference (as we aren't sure what the problem is), but it really can't hurt to try.

If he has a lot of hair on the bottom of his feet, it may help to carefully cut that out, along with the dark stuff? Don't get carried away with the scissors... no 'snip... snip' approach! Sometimes you can only cut a few hairs at a time, in order to make sure you don't have some of the web between his toes in the tips of the scissors. Small scissors work best for most people.

I agree with what has been said above, like Shazzy I use salts as a cure all. Epsom or sea salts I have found work the best. You can get them at wal mart for $1.97 for a big bag :)