Marine aquarium grade acrylic

Hey all...

I have been looking into the idea of making my own sump and overflow
box out of acrylic, but all three local plastic dealers told me that
acrylic is not suitable for constant suse in water due to it being a
thermoplastic and its water absorption properties. I live in th UK and
one of the biggest producers of acrylic here is a brand called
Perspex. I'm not sure if they operate in the USA, but can anyone tell
me if their acrylic suitable? I have tried emailing them on a couple
of occasions, but never had a reply. I have been told that almost 90%
of marine aquariums in the USA are made from acrylic and wondered if
there was anyone who knows what I shoul ask for when looking for my
sheet materials.

I also need to know if regular acrylic adhesive will be suitable to
make the joints with, or is there a specific adhesive which is 'marine
safe'. If I use regular ahesive and use a very salty or brine solution
to wash the sump out, will this sufice?

hopefully someone can help me!

Thanx