I never give up and I never let anyone get by with charging me for something I didn't receive....even if it's only $1.00. Might be my age.
From your decription, he didn't send you what he advertised. If they were supposed to be on mats/mesh and weren't, you have grounds to get all of your $$ back. PayPal is very clear on that. So go for it!
And don't email him any further; just file a dispute and let PayPal handle it. But do keep his emails to send to PayPal if requested. And don't wait too long; PayPal only gives you 45 days and some sellers will try to string you along until the 45 is over.
And in future, I can recommend www.plantedaquariumscentral.com
and "peachii" on this forum for quality service and plants.