I think there is a great possiblity to succeed. There are too many shopping centers in Doha but aquarium shop, not many. and the aquarium stuff there is expensive, if you could get a wide range stuff with acceptable quality and reasonable price, you will have a great market here.
Of course that you look into the market here in Doha personally will help you a lot.

(I am in led industry and I am planning to have a led aquarium light light business in Doha.)