This tank is awesome too. IMO, forget the co2 if the shrimp are your priority. It just adds another thing that is making them unhappy so if it's not necessary leave it be. Nice find on the 2213, you will be very happy with it. I couldn't do an Iwigumi tank, I love lush thick plantings and Iwigumis are to minimalist for my taste.
Kiran-the double taps/quick disconnects are on the Eheim Classics and are what you use when its time to do filter maintenance. You close them them then unscrew them co cut the water off from the intake/outflow and also from the filter. You can also use the valve on the outflow to control the flow by turning it down to your desired level of movement.