What should I put in duck run for bumblefoot

[Duckpooper]

Alot of my ducks recently have been getting bumblefoot. I have 11 ducks and 4 of them have had it so far, and my oldest is only a year and a half. They have a 28ft by 9 ft duck run, with only a 4x5ft patch of grass, sand in the area I put them at night, and a large pool. The ground is quite hard(which is probably why they keep getting it), and I'm not sure what to put in it since I live in Arizona and growing grass is quite hard here(and expensive). I've been hearing pea gravel is good to put in there, but I'm afraid it'll get too hot since today was 115 degrees f. Any suggestions will help greatly!

 

[416bigbore]

Can you post pics of the bumblefoot.

 

[Weeg]

Hey are probably getting bumble foot from getting cut and infected. Or they are getting thorns or splinter in there foot, which causes the bumble to form. I don't know anything about the ground causing bumble foot, but I would check for anything that might cause splinters or cuts.