I don't know of any discounts, but they do have a loyalty points scheme of some kind. I have bought quite a bit from them now and they have always been prompt and very helpful. I haven't bought plants. Just tank, hardware, accessories, chemicals, etc. I have always been happy.
Was good for the fish tank which only took 2 days and wasn't broken, was bad for a thunder shirt which took two weeks. So hit and miss, but good for the tanks I think