Anything that says "First aid for ingestion: DO NOT INDUCE VOMITING" gets a no vote from me. That's generally the recommendation for things that are corrosive or otherwise cause tissue damage on contact. In other words, stuff you shouldn't have placed in your mouth in the first place.
That container looks like polyethylene, which is slightly porous. It can absorb and retain some chemicals in spite of repeated cleanings. Ever see a Tupperware container stained by tomato sauce? Same effect.
Without more information on what was in that tank, I'd give it a pass.