pico/nano idea

[grumpy_banghai]

I'm thinking about setting one of these up in a bedroom.

http://www.practicalfishkeeping.co.u...t.php?sid=2705

I'm planning to fit a larger HOB filter & house the heater, LR rubble, Floss & cheto inside.
Maybe an Eheim 2042 or something. What's the smallest heater I could use to place in the compartment?
Planning to house a few frags on a few KG of LR, cleaner shrimp & a goby.

[cl0wn]

cracking price for the tank, nice little project.