for the light's waterproofing....... plexiglass and a lot of caulk.as for the whole idea of flushing the reservoir every time you flushed the toilet, that would be absurd!!!!! dwc with a small reservoir, should do the trick adn make them bushy but small. thinking of keeping a grow log of two i a toilet but i dont wanna start until i select a good strain or a good one to order and save up the cash.