My GCSE German is long-forgotten, so I just used Google translate
The Lunapet regulator I linked to comes supplied with a needle-valve, so you won't need to order one.
The needle valve is attached to the regulator and provides us with a stream of bubbled co2 from our supply.
I'm just learning the game and don't have enough experience of the internal diffuser v external reactor choice to give advice, but I did my research before obtaining my hardware, and I ordered one of these Rhinox 5000 diffusers, for my 350 litre tank) from Aquaticmagic:
http://cgi.ebay.co.uk/Rhinox-5000-Glass ... m153.l1262
...however, I decided to go down the external reactor route to simply minimise the equipment in the tank.
You can see the external reactors (reacktoren) on the lunapet website
http://www.lunapet.de/co2aktivaussenrea ... p-147.html but decided to build my own. There are a few pics on this thread:
viewtopic.php?f=20&t=3871
I don't regret getting the Rhinox 5000 as it will act as a reserve/back-up, just in case I have a problem with my external reactor.
You'll also need a drop-checker. Have a read of this really good article
http://www.ukaps.org/higher-tech-tank.htm
Again, I got my drop-checker from Aquaticmagic,
http://cgi.ebay.co.uk/Chameleon-Drop-Ch ... m153.l1262
......... and 4 dkh solution from aquaessentials:
http://www.aquaessentials.co.uk/index.p ... ts_id=1977
That's all I can think of in terms of CO2 hardware, but speaking as a newcomer to the 'high-tech' part of the hobby, I would recommend you read the excellent articles here
http://www.ukaps.org/articles.htm
Don't worry if you don't take all the info in after the first read. I had to read each one a couple of times to get the concepts right in my head.
Hope this helps, and let me know if you want any clarification.