Thanks for the suggestions - I did Sumida Aquarium and Aquaforest in Shinjuku, very close to my hotel!
Amano's aquariums in Sumida were the first thing you see when you go through the ticket gate. I wish I could upload photos now but I'm still in Thailand without a computer for another week yet. I promise photos next week though! The tanks were nice, but maintenance could have been better! The 2 smaller tanks were to the left of the room (maybe 5' square and 2' deep as a guess), and there was one similar to his home tank straight in front of you. The very long tank covered the length of the wall to the right, and there's another behind you to the right (quite a poor layout and poor health in this one). The others were really nice layouts, although could do with a clean! Great to see overall though.
Aquaforest Sinjuku is hidden in an underground mall called Subnade, near the subway, and was incredibly hard to find!! I got there eventually though, and it as reall worth it. For a relatively small shop, the range of fish and plants available was very good, and there were a good amount of ADA products at way less than half the price we get in the UK. I bought some Do!Aqua tools, a CO2 diffuser, and even got some sand it was that 'cheap'. Saved about £100 on home prices. The 3 liter bags of Aquasoil were around £6 each too. Was almost tempted to buy a several bags and get another suitcase to take it home in! Anyway, that shop is well worth a visit if you're ever in Tokyo. I think I got some nice pictures there too on my two visits, so ill upload those next week too.
Tom