excel and vals are ok...as long as you dont overdose it. or it will melt like others experienced. vals can melt when first planting. just leave it alone and once it acclimates to your tank and starts taking off they go crazy.
I had this happen yesterday - it looks like the tips are the only thing that have melted. I'm just going to follow the advice and cut the melted parts and do a water change. Bumber, my Val's were just starting to curl over to the other side of the tank like I wanted them to.
You can acclimate Vals to Excel dosing. You just usually have to slowly work up to full dose. Once acclimated they seem to do fine even with a bit more dose then Excel recommends. I've never dosed much more than that so don't know if that would help protect them if overdosing for algae problems though.