I have to say that .in all the MA stores I visit.The morden one is the best I've seen staff wise.....they really do seem to know what they are talking about and the fish there are very healthy looking.I shop at MA in Morden frequently and have seen them talk themselve out of sales to people who did not have the correct set up to look after the fish. They have some experienced, knowledgable and helpful staff there, but like any shop you'll always get one or two that aren't up to scratch.
They have several arrowanas there and they display a green with a certificate.The owner of the fish(also the fish house manager) prices all his arrowanas off the scale to ensure they are going on to a deserved home. His "green" is for show and not for sale!!