Still get non-positive values for the 'gamma' family I am going to post it here, as suggested in stackoverflow:
I am analyzing percentage data with glmer, and I have read that Gamma family should be suitable for this kind of data. I have checked my data and there are no values below 0, but I still get an error saying I have non-positive values.
  > summary(total_F$p.prcnt)
       Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
       0.00   50.00   75.00   68.56  100.00  100.00 

Just adding my code, that i used:
F_par1<- glmer(p.prcnt ~ b.element+distance+b.element*distance +year+sampling.round+(1|LS1),  
                   family = Gamma, 
                   data=total_F)

What are my options? I tried to modify my data in Excel to be proportional and use binomial, but I would prefer to use Gamma, if possible.
EDIT:
I cant also remove the zeros, as they are meaningful

The gamma distribution has its support on the positive axis. Data generated by a gamma will be positive with probability 1. Essentially, a zero value can't come from a gamma. So the gamma is not a good choice for your data. ("Percentage data" sounds like it might be bounded at 1, too, which would be another reason not to use a gamma, because its support is unbounded to the right.)
You might want to look at zero-inflated models. The zero-inflated gamma is sometimes used, I just don't know a way of dealing with it in the context of a mixed model.
