Look for a used one first and for most as they can be picked up pretty cheap. Brand is a personal prefrence, but I like GEO's. If you are using a controller like apex or reef keeper, then any regulator with a solenoid will work on the C02 tank. or without controller, then a good solenoid with a bubble counter will work.
Here is what you need.
Regulator and Solenoid with out a Bubble counter
OR
Regulator and Solenoid with Bubble counter
and
C02 Tank, that can be picked up from a local gas retailer or bought empty online. I just got one from AirGas.
And
And Finally the media. I use Reborn and it seems to be the best out there at the moment.
Here is what you need.
OR
and
And
And Finally the media. I use Reborn and it seems to be the best out there at the moment.