Acrylic welding with Methylene Chloride

[WarDog]

I went to Industrial Plastics and Paints today to pick up the supplies for my aquascaping. 1/2" acrylic rod and some off-cuts of acrylic sheet. Also picked up some Methylene Chloride and a nifty little applicator for welding. The guy asked me what I was using it for and I told him about my build. He said Methylene Chloride was not reef safe and after time could leech into the tank and cause serious harm... so I'm a little confused.

Isn't that the standard welding cement everyone uses for acrylic sump builds?

Should I or shouldn't I use Methylene Chloride for welding acrylic?

Never welded acrylic before so I'm a little stumped.

Thanks for the input.