well your biggest problem is the heat signature given off by all the heat buildup. If a police chopper does a fly bye and sees that heat, your done for!
(remember that the police scanner can only pick up the heat signature directly on the surface of objects) So if you run cooling pipes on the ceiling you can remove that risk.

secondly if your doing a hydro system for that large of a room, its going to be very very heavy I dont not recommend put your res. tanks up there unless you really reinforce the structure.

third, I recommend making a hidden staircase for easy up and down access. unless you really want to build those muscles climbing a ladder many times a day

most importantly humidity control, you'd be surprised how fast mold grows in an attic.

besides those, its really just like any other setup... measure and plan out the system before you build the rooms...







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