new tank setup

[nel3]

i have fin rot for my DTHM dorsal tail. i went to the pet shop to get a 4th heater for QT tank purposes. 75$ later i leave both stores with a heater, 2.7g KK and decoations for it. i 'll put the DTHM in my 1g QT and get my CT out of the 1gal. i now have 2 QT tanks for my fish, 1 heated 1g and an unheated .5g.

my question is whats the best method to get a heater access slot on the lid? atm i just put the heater through the square and set the lid ontop of the heater cable. i'll put a weight on top of the lid for the time being until a better solution comes up.