A few years back, I built a computer into a small fish tank to see how it would look/work with the mineral oil. I used cheap parts because I didn't want to ruin expensive ones on a random project. The computer sits on my desk at school (I'm a teacher, last two images) and students always ask about it and ask why I don't have fish in it. So I explain that its mineral oil.. blah blah blah. This gave me the idea of wanting to find a way to have a computer in mineral oil with fish around it. GIGABYTE beat me to it with their build but this summer I did finally get to build my version of it. This also gave me an opportunity to solve a few issues I had with the first fish tank. One of these issues was oil wicking. Oil would travel along the wires coming out of the tank and make a mess on the power cable and the hard drive. To solve this, I actually cut the power cord down and plugged it in to an extension cord. This breaks the suction and the oil does not continue down the extension cord. Another issue was that I forgot to take all the stickers off the hardware. Mineral oil eats away the adhesive so the stickers end up curling and falling off.
I had originally wanted to make the inner tank out of plexiglass but when I tested my creation with water, the seals blew out. Wasted some money to decide it was just easier to buy a smaller fish tank and prop it up on plexiglass supports. The computer is in the small tank, covered in mineral oil. Surrounding the tank is water with my turtle, Emerald, and some small fish he hasn't managed to catch yet. I have a couple USB LED light strips along the front rim of the 75 gallon tank to give the tank a cool look. The part list doesn't have the prices anymore but the R9 Fury X came from another build. The rest I bought new for this build on Newegg.com.
My plan is to use this computer as a media server holding files for access from my home audio system and other computers in the house. I built it more as a conversation piece than anything else as it resides in the entry way of my new house.