Hey Vio this is the tank that I have been working on and this is the reason why I am not able to work on my led fixture. Once I fill this tank with water and everything is safe and find no leaks I will be able to work on the light.
Blue stuff is Dura Rubber and I bought this from http://www.rubberizeit.com and originally it comes in White color but I gave them this color code and they made this for me at no charge. Great stuff and their team is very helpful if you have any question just call them or email them and you get call or email back within hour or so...
Thank you for info. one more Q, the glass is 3/8 ?!