cutting rottin roots GOT PICS

I WAS CHANGING THE REZ WATER. and i seen that my root rot was getting bad i got new root growth cause u can see the nice white roots.and i got me some hydroguard.but i did cut the old nasty shit away.not short if thats cool.if some one could shine some light my way.it would be great.here are the pics

You need to put an air stone in the resevior and push some fresh air down there. This sort of root rot is usually caused by a lack of oxygen.