Those pictures really drive the point home about avoiding using a galvanized stock tank without a liner at all costs.
I almost did that a while ago, but I found out here on MFK that it would eventually kill my fish, so I decided against using it by itself then added a liner. I thought that everything would be fine, then some chemical from the supposedly "fish safe" liner ended up killing the fish faster than the zinc would have... Just like you, I lost some really nice fish as a result of their container leaching something into the water that proved to be deadly. Sorry for the slight derail, but I definitely know where you're coming from on this one.