Worst possible word or phrase you can call a person. To be pond scum is be worse than any curse you can dream up. Pond scum is the shit of humanity. The worst of the worst and nothing can get any lower than this. Pedophiles, rapists and any kinds of abusers would be worthy of this title.
Rehmeyer was considered pond scum after abusing children and women.
What's the lowest thing you can think of? Pond scum! What could be the answer to the energy crisis? Pond scum! Turns out that algae (pond scum) is an excellent source of vegetable oil, which can be turned into bio-diesel and used in place of petroleum based diesel fuel. What a bargain!
1st person: Hey, let's start an algae farm and get in on the pond scum business before it even starts!