Thanks for the response and interest!
I'm planning on ignoring everything about the filter media provided and will do my own thing. But yes, a simple idea to save shrimp is put the filter right next to the intake bit.. I hadn't thought about that and was already thinking about adding mesh... your idea is much better and straightforward.
In regards to heater, where we are in Australia it gets 40 degrees in summer, but we had -7 last week at night.. this morning was a much warmer -3! The heating in the office is a bit whack too... it seems to be boiling hot or freezing cold, so the heater is something i'll just play 'wait and see' with. I don't propose to stock for a while anyway so will have substantial time to monitor the temperature and see if/how/when a heater is needed.
I saw a short youtube video on the water level at the back.. I'm glad I watched it / you told me because if I went in without knowing I'd be freaking out the first time I noticed it.