I have gaps in this cover's sealing, because of torn rubber gasket:
You can see gap between cover and aquarium's body it seals to:
Aquarium shop seller told me that i don't need special hardened silicone to pull this off so i bought this aquarium-safe silicone:
Text is in hebrew but if to translate to english, it goes like this:
Silicone For Aquarium
Absolutely non-poisonous
Stays transparent and flexible
Highly resistant against sun rays
Perfect adhesion to glass
Do you think people this will work? Maybe there is aquarium-safe hardened silicone that after smearing hardens and creates hardened gasket? Now why i keep mentioning "hardened"? Because i don't want to remove (or scrape?) silicone every time want to disassemble cover to change fluorescent bulb (yes there is a bulb inside) or to clean inside, so i thought about having hardened gasket to use time and time again as i assemble and disassemble cover.